Large Women and Prenatal Testing:


by Kmom

Copyright 1996-2004 Kmom@Vireday.Com. All rights reserved.

This FAQ last updated: May 2004

DISCLAIMER: The information on this website is not intended and should not be construed as medical advice. Consult your health provider.

SPECIAL NOTE: This FAQ mostly concerns only basic amniocentesis information and how amniocentesis impacts women of size.  For more complete information about amniocentesis, see the FAQ, An Amniocentesis Primer, on this site.  Kmom STRONGLY URGES women to read the full amniocentesis FAQ before reading this FAQ.  



"The technology of prenatal diagnosis is usually presented to us as a solution, but it brings with it problems of its own...the technology of prenatal diagnosis has changed and continues to change women's experience of pregnancy."  

---Barbara Katz Rothman, The Tentative Pregnancy


All pregnant women in our technology-happy modern society face confusing choices about prenatal testing, its advantages and disadvantages, and its appropriateness for them. Large pregnant women face even more confusion, since prenatal testing can be slightly harder in this population, and the results can be more confusing. However, since they may be at a somewhat increased risk for problems like neural tube defects, they also face greater pressure than others to have these prenatal tests, even though the tests are often difficult to interpret.

This section is an attempt to present an overview of the most basic prenatal tests most pregnant women in the US are pressured to have, including Ultrasounds, the AFP/Triple Screen Test, Gestational Diabetes tests, and under certain conditions, Amniocentesis.  It is further designed to address the special concerns that large women might have in taking these tests---their fears, any special equipment that might be helpful, the controversies over interpretation of results, whether large women have a higher rate of so-called 'false-positives' on certain tests and why, etc.

It's important to remember that discussing prenatal tests can be simple or incredibly complicated, depending on the degree of detail that is needed and the point under discussion. This FAQ is NOT intended to be a full explanation of all the intricacies of taking and interpreting various prenatal tests, but rather a discussion of them as they pertain to large women instead. A brief description of the test, its purpose, and the procedures are given for each, but the majority of the information is about the specifics of large women and the test. If you need more detail about statistics, interpretation of results, rates of 'false-positives', etc., then be sure to research the many websites devoted to prenatal testing online.

It is also important to realize that most women take these tests without fully considering all of the implications of the test.  Most women think of these as a simple blood test, a cursory part of prenatal care.  They don't consider that intimately wrapped up in the question of prenatal testing is the moral dilemma of abortion and the thorny issue of eugenics. Barbara Katz Rothman points out: 

The history of prenatal diagnosis has roots in the eugenics movement...part of its history has been an attempt to control the gates of life: to decide who is, and who is not, fit to make a contribution to the gene pool.

Katz Rothman is by no means arguing against the use of prenatal testing; she actually presents a number of compelling reasons to consider it.  Her writing is a fair and balanced look at the intricacies and difficulties of this issue.  But she has found through extensive interviewing of parents involved in such testing that most of them were simply unprepared to confront the scope of the types of decisions presented by prenatal testing, and that choosing such testing often changed the way a woman experienced pregnancy in subtle ways.

Parents who are considering using prenatal testing need to be sure they really understand the following issues BEFORE the test takes place: 

More on these kinds of questions is available on other websites about prenatal testing, but it vitally important that parents think about these issues BEFORE they decide whether or not to test.

Readers may feel that there is a strong anti-testing bias in this FAQ.  Kmom's own experiences with prenatal testing (detailed below) have largely been negative, and she is certainly strongly concerned that so many women enter into these tests without really considering what they are doing beforehand.  Part of the purpose of this FAQ is to help women understand the scenarios they might face should their screening test come back positive for possible problems.  And because the overall bias of our technological culture is towards doing more and more testing, she feels an extra responsibility to challenge the automatic assumption that more testing is better.  

However, by no means is she condemning testing completely, nor does she criticize those who do choose to test.  Prenatal testing has certain advantages and in some situations can be a great help.  And under certain circumstances, Kmom would choose to use some of it too.  She is simply pointing out that the issue is far more complex than most clinicians would have patients consider, and that parents need to ask themselves the hard questions before they begin the process.

Finally, it's also important to note that none of these tests are mandatory. Although many women are simply told that they will be taking these tests, it is ALWAYS your right to decline any or all of these tests. Just because you are 35 or over, for example, does not mean that you HAVE to have an amnio, and just because you are a large woman does NOT mean that you have to have the AFP test or gestational diabetes test.  Conversely, it is also your right to request certain tests if they are important to you.  

You have the right to accept or decline any test or treatment during pregnancy. It is YOUR body, and YOU have the ultimate choice. Research the issues carefully so that you make an informed choice, and then either request or decline the test, based on your individual needs and values. Don't let any provider try to bully you into (or out of) tests---listen to their counsel, do your own research, and then MAKE YOUR OWN CHOICES.



*Note: This section is a repeat of the first section of the Amniocentesis Primer FAQ.  If you have already read that FAQ as recommended, you can skip down to the next section of this FAQ.

Amniocentesis is the process of inserting a needle into the uterus to withdraw some amniotic fluid from around baby for testing.  This amniotic fluid can then be used for testing for certain conditions or birth defects in the baby.  

Complications of amniocentesis can include cramping and bleeding, amniotic fluid leakage, and miscarriage/fetal death.  More unusual complications include fetal respiratory problems, birth defects, uterine infection, and rarely, maternal death.  Because of these potential problems, risks and benefits from amniocentesis must be weighed carefully before making a decision about doing one.

In Kmom's personal opinion, it is wise to be very cautious in deciding to do an amniocentesis. However, each person must weigh the benefits and risks of any procedure and decide for themselves what to do.  In certain situations, it can certainly be a useful test to have.

What An Amniocentesis Does

An amniocentesis uses a hollow needle to remove amniotic fluid from around the baby. This fluid is then cultured, the chromosomes mapped ("karyotyping"), and the fluid tested for various diseases and problems.  

The FAQ on amniocentesis at sums up what an amniocentesis is used for:

[Chromosomal mapping] allows the detection of trisomies (extra chromosomes), monosomies (missing chromosomes), and other structural defects in the chromosomes. Most people have 46 chromosomes, in 23 pairs, but some have an extra copy of one chromosome, called a trisomy because there are three of one chromosome pair. This extra chromosome can lead to a variety of abnormalities. The most common trisomy is called Down syndrome, a trisomy of chromosome pair 21, and it leads to mental retardation and various physical problems. Other common trisomies are trisomies 13 and 18 (which generally cause a baby to die shortly after birth) and sex chromosome trisomies.

Examining the chromosomes also allows the sex to be determined, which may be of particular interest to women who are carriers of sex-linked disorders, such as hemophilia or Duchenne muscular dystrophy. 

In addition to examining the fetal cells for chromosome abnormalities, the amniotic fluid can be tested for levels of [AFP], acetylcholinesterase (AChe), and hemoglobin F. It is possible to detect neural tube defects, including anencephaly, spina bifida, and meningomyelocele (though the use of amniocentesis to detect neural tube defects has been mostly superceded by a combination of the AFP test and high resolution detailed ultrasound). 

It is also possible to detect about 70 metabolic disorders. The tests for metabolic disorders, however, are only done if family history warrants, and will not be done for women being referred for amnio due to age or results on the AFP test or Down's screen. If there is no history of genetic disease in the family, a genetic analysis will not be performed, only a chromosomal analysis. Chromosomal analysis is performed at most large hospitals and some private labs. Genetic analysis is only performed in a few labs in the country and is significantly more expensive. 

Amniocentesis to diagnose birth defects is usually done between the 14th and 20th weeks of pregnancy, most commonly at weeks 15-16.  Amnios can also occur in late pregnancy to test the maturity of the baby's lungs if early delivery is being considered for some medical reason.  Occasionally, amniocentesis is used for other reasons as well.

However, most commonly, amniocentesis is done to check for birth defects and other problems in the baby.  Parents must remember that it does not detect ALL birth defects, and a "normal" amniocentesis does not guarantee a "normal" baby.  For chromosomal disorders, it is a very accurate test, but one that is not without potential risks.   

How An Amniocentesis is Done

In an amniocentesis, the mother is generally given genetic counseling first to try and clarify the parents' genetic heritage and any possible genetic risks. It is a good idea to have researched your family history as much as you can ahead of time, before the genetic counseling appointment.  

Mothers having an amniocentesis should be sure to get plenty of fluids in the week or so before the test.  Poor maternal hydration can sometimes decrease the level of amniotic fluid in the uterus, and this in turn could make getting enough fluid for the test difficult.  Good hydration may help increase the level of amniotic fluid and make it easier to get enough.  In addition, the targeted ultrasound just before the amniocentesis may be helped by a bit of extra fluid in the bladder.  Therefore, it is probably a good idea to be well-hydrated before the test, but you don't need to drink excessive amounts.   

After genetic counseling, a "level two" ultrasound is then done to check for any signs of fetal abnormalities, to check the baby's heartbeat, to determine the position of the baby and of the placenta, to examine closely the main fetal structures, and to double check the baby's gestational age.  A "level two" ultrasound does not mean that any special equipment or intensity of ultrasound is used; it simply means that they take more time to do the ultrasound and are looking more directly for certain problems.  This is often referred to as a "targeted" ultrasound.  

Ultrasound is used to determine the best location for placing the needle---a pocket of substantial amniotic fluid well away from the baby and umbilical cord.  When amnios first came into use, they were done "blind" (without continuous ultrasound guidance during the amnio), and this resulted in a number of disastrous outcomes, including occasional cases of horrifying fetal damage and death.  Modern amniocentesis is done with continuous ultrasound and is much less dangerous.

Continuous ultrasound during an amnio allows the doctor to see a constant view of the needle's path and where the baby is located at all times.  If the baby moves near the needle's path at any point, the doctor can then reposition the needle, or if necessary, withdraw the needle and try again in a different location. Continuous ultrasound has eliminated a great deal of the risk formerly associated with amniocentesis, but at times babies still do get "stuck" by amnio needles.  Rarely is it serious, however.

For the amniocentesis, the mother lies flat on her back on a table.  Iodine solution is swabbed onto her belly in order to cleanse the area thoroughly, and sterile drapes are placed around the area.  A local anesthetic may be used to deaden the area where the needle will go in, but is often not used since the pain is usually minimal and a local means administering a second needle insertion.  A thin, hollow needle is then inserted into the abdomen and uterus, using continuous ultrasound to guide the process.  

In mid-second trimester amnios, about 2 tablespoons of amniotic fluid are removed through the needle; in first-trimester amnios (now not usually done), a little less is removed in order to minimize any possible effects on the baby.  The first bit of amniotic fluid is discarded so that the chances of contamination with the mother's blood or cells is minimized, then the rest of the fluid is removed.  This part of the process only takes a few minutes if everything goes well.  

After the fluid sample is taken, the doctor checks the baby's heartbeat to be sure all is normal.  The fluid sample is then sent off to a lab to be analyzed. The mother's body is thought to replace the amniotic fluid within about 12 hours to a few days of the procedure.   After the amniocentesis, most doctors recommend taking it easy for a few hours or a few days.  Most tell the mother to avoid lifting heavy objects and prolonged standing.  

Living cells from the fetus exist in the amniotic fluid, and these cells are grown in a laboratory for one to two weeks.  These are then tested for chromosomal abnormalities and sometimes for various genetic birth defects. Results usually can take one to three weeks to arrive, although they average about two weeks in most cases. 

The levels of alpha fetoprotein in the amniotic fluid are also checked for the possibility of neural tube defects.  Because this can be measured directly from the fluid, without any culturing, results of this test may take only a few days.  This test may be even more accurate than the AFP/triple test that is done from a maternal blood draw but some research suggests that its use has become outdated and unnecessary.

There is a new method of analysis for amniocentesis that reveals results faster, but less completely.  This is called Fluorescent In Situ Hybridization, or FISH.  According to Mark Perloe at

[FISH] involves using special dyes targeted to specific chromosomes.  Each dye glows a different color under fluorescent lighting.  At present, we can only test for four or five different chromosome pairs using this technique.  Normal cells have 23 pairs of chromosomes; an abnormal fetus may have an extra chromosome or may be missing one from a pair. Since we can't test all the chromosome pairs using FISH, this method only picks up a portion of the potential chromosomal anomalies that may occur.  Luckily, the most common problems are picked up using this screening method.  As results from this test can be available within a few hours, FISH is gaining in popularity.  

What An Amniocentesis Feels Like

Many women worry that an amniocentesis will hurt.  Most literature on amniocentesis tells women that it will not hurt at all, or that it will only hurt a tiny bit.  Dr. Marjorie Greenfield at states, "This procedure...hurts only a bit more than getting blood drawn, and less than getting a shot, or having an IV started."

Actually, women's experiences vary quite a bit.  Some women report that the amnio didn't hurt at all, some women report only a feeling of significant pressure (especially when the amniotic fluid is being withdrawn), some women report a feeling of cramping when the needle goes into the uterus, and still other women report that the amniocentesis was quite painful.  

Kmom's Story: My amnio certainly hurt more than "getting a shot or having an IV started."  Putting the needle into the skin felt about like getting a shot, not too bad.  When the needle pierced the uterus, though, it was definitely painful, about like a very strong menstrual cramp---painful, but tolerable.  

However, because the baby moved, they had to withdraw the needle and re-insert it a second time.  This time the procedure was definitely very uncomfortable, probably because I had a contraction during the insertion and it was difficult to get the needle in. In order to get the fluid out, the doctor pushed very very hard on me and I felt great pressure as he tried to withdraw enough fluid for the test.  At that point, it was definitely extremely uncomfortable, even painful, and the atmosphere in the room was very tense. Eventually they got enough fluid for the test and withdrew the needle.  What a relief when it was finally gone! 

My amnio experience did cause me significant discomfort/pain, much more than "getting a shot" or "getting blood drawn."  However, I also know women who have said that the procedure did not hurt at all.  In all likelihood, the experience varies according to the skill of the doctor and the circumstances of the amnio.  The fact that I had a Braxton-Hicks contraction during the amnio probably was a significant part of why my experience was painful.

Most doctors also probably underestimate the amount of discomfort involved in an amnio.  Even so, usually the procedure is not as painful as most women anticipate it will be, and many women report that the experience was only mildly uncomfortable.  However, each woman's experience is different and depends on a number of different variables. 

After an amnio, most women experience at least some degree of cramping.  Most doctors recommend resting until the cramping has subsided, and taking it easier than usual for the next few days.  Avoid heavy lifting during this time, even if you are feeling well and have had no spotting or cramping.  Within a week or so, you should feel back to normal or very close. 

Possible Problems During the Amniocentesis

Most of the time, amniocentesis goes quite smoothly.  But some of the time, amnios can become more difficult, or may encounter significant problems during the procedure.

Several factors may be more predictive of a difficult amnio procedure.  These include uterine fibroids, low amniotic fluid levels, a retroverted uterus, maternal obesity, and past history of vaginal bleeding in the pregnancy (Johnson 1999).  However, many people with these situations have had an amnio without problems, so these factors do not always signify that there will be problems.

Sometimes more than one needle insertion must be used.  If the baby moves near where the needle is going in, the needle may have to be pulled out and reinserted in a different spot.  Or the spot they selected may not be turn out to be very good and they must try again.  

Sometimes the doctor has difficulty getting the needle in, especially if the mother has a Braxton-Hicks contraction before or during the procedure [as happened to Kmom, see above].   Sometimes a problem known as amniotic membrane "tenting" occurs, where the membranes resist penetration by the needle and are pushed back but not penetrated by the needle.  This may be more associated with fetuses with chromosomal abnormalities like Down Syndrome, but also is more common in earlier amniocentesis procedures (Johnson 1999). 

Sometimes a "bloody tap" occurs, where blood is found in the amniotic fluid.  This blood may be from the needle insertion in the mother, it may occur because the placenta was encountered, or it may come from the fetus.  Blood-stained amniotic fluid is generally associated with more complicated and problematic amnios, but by itself is not a cause for immediate alarm.  In other words, problem amnios have bloody taps associated with them more often, but a bloody tap alone does not necessarily mean there will be problems.  

Every needle insertion raises the risk for problems so it is best to avoid multiple insertions whenever possible.  Most doctors will only do two needle insertions in one amnio session; if they cannot get good results in two insertions, they will often tell mothers to come back and try again in a week or so.  If the first needle insertion goes badly, mothers may want to consider whether to continue the amnio at all. Certainly if success does not come after two needle insertions, the amnio should probably be abandoned that day and, if desired, tried again later.

Sometimes the doctor seems to complete the amnio just fine but later finds out he did not get enough fluid, or the fluid is contaminated by blood or maternal cells.  In this case, the mother will be called to come back for a repeat amniocentesis.  Another possible problem occurs when lab workers are unable to culture enough cells from the amniotic fluid to do karyotyping.  This would also  necessitate a second amnio. 

Needing a repeat amnio because of culture failure is thought to occur about 2%-6% of the time in second trimester amnios, and up to 18% of the time in first-trimester amnios.  Sometimes culture failure is more common with certain fetal abnormalities, but most of the time the baby is normal and the lab just needs more amniotic fluid with fresh fetal cells.

Repeat amniocentesis happens more often than people think. Barbara Katz Rothman, author of The Tentative Pregnancy: How Amniocentesis Changes the Experience of Motherhood, found that 10% of the women having amnios that she interviewed ended up having more than one amniocentesis. The medical literature reflects smaller numbers (especially for second trimester amnios), but even so, the numbers are still significant.  The possibility for needing a repeat amnio is one of the risks of amnios that women are rarely adequately informed about.

Again, remember that at any point, you can decide not to continue with amniocentesis. If problems are encountered during the amnio or a repeat amnio is needed, some women choose to just stop the process altogether, or to stop it and wait a while before trying again.  The decision is ALWAYS up to you----it is your body and your baby.  You have the ultimate power to decide whether or not to continue. 

Possible Problems After the Amniocentesis

According to the March of Dimes, about 1-2% of women experience cramping, spotting/bleeding, or leakage of amniotic fluid after an amniocentesis.  Anecdotally, the rates seem higher when talking to women who have been through amnios.  

Most women report some feelings of cramping after an amnio, though the cramps are usually mild. Spotting is more unusual but does still happen to some women.  Leakage of amniotic fluid seems more rare, anecdotally, but it may not be easy to spot this if you are already bleeding.  

Be sure to call your doctor if you have any concerns.  According to various amniocentesis resources, you should contact your healthcare provider if you experience any of the following after an amniocentesis:

It is better to err on the side of caution.  If you experience any problems after an amniocentesis, call your doctors right away and keep them informed.  They can track your symptoms and advise you what to do.  Don't worry about "bothering" them or think that your symptoms are too trivial to mention.  Doctors need to stay fully informed of your condition so they can assess how you are doing and what to do about any problems.

If you are feeling very ill or have symptoms of an infection, don't hesitate to go to the Emergency Room immediately and get checked.  Be sure to let them know you had an amniocentesis.  If you show any signs of infection, you or your partner may need to get assertive in order to get them to take the possibility of infection seriously.  Although medical personnel may discount the possibility because it is rare, infection is a major risk of amniocentesis, and one that can kill (and has).  Be assertive about getting treatment if you suspect you may have an infection. 

Although miscarriage after an amnio is thought to be most common shortly after the procedure, some research indicates that it can still happen even 6-7 weeks after the procedure.  If you do experience problems, even weeks after an amnio, be sure to mention to your health care providers that you recently had an amniocentesis done.  


Large Women and Amniocentesis

What about obese women and amniocentesis?  Are they at increased risk for miscarriage or other problems?  Is any special equipment needed for amniocentesis in very large women?  What ideas may help make an amnio go more smoothly in a woman of size?  

Obesity and Amniocentesis Risk

The implications for larger women and amniocentesis safety are unclear. Physically, the test is harder for the doctor to do on larger women because abdominal adiposity (fat) may make uterine access more difficult.  This increased difficulty may be associated with a higher rate of problems getting enough fluid or perhaps with the need for more than one needle insertion.  

However, although there is some increased difficulty in doing amnios on larger women, it is not that hard.  Most large (even supersized) women have normal experiences with amniocentesis.  If you choose to have an amniocentesis, chances are that everything would be fine.  However, it is possible that it may be more difficult and slightly more risky.  

Several online resources suggest that obesity may increase the risks of amniocentesis.  Unfortunately, it is difficult to document whether obesity truly increases the risks of amniocentesis because most resources simply state that it does without any discussion or references to back up this assertion.  It certainly seems possible that obesity might increase the risks of amniocentesis, if it is harder to get enough amniotic fluid or if multiple needle insertions are required.  

Johnson (1999) suggests that in Early Amniocentesis (performed in the first trimester), an increased Body Mass Index (BMI) was associated with a higher rate of fetal loss and amniotic fluid leakage, among other many other factors.  They note:

Maternal factors found to be independently predictive of fetal loss included increased BMI...Increased BMI was also a predictive factor for a 'difficult procedure', which in turn was associated with an increased risk of fetal loss.  This implies that maternal obesity likely imposes technical challenges to the operator, increasing the probability of a difficult procedure and of post-procedure complications. 

In Johnson's study of the risks associated with Early Amniocentesis (compared with mid-second trimester amniocentesis), obesity was definitely associated with a dramatically higher rate of fetal loss, especially as Body Mass Index increased.  However, the numbers of losses in the mid-second trimester amniocentesis were not high enough to allow a similar comparison to be made for the later amniocentesis group.  So we do not know for sure whether the risk for fetal death is higher in women of size during all amniocentesis, or whether this effect is limited to Early Amniocentesis only.   

Another factor that studies may fail to control for is the past history of infertility and/or miscarriage.  Larger women, especially those with Poly Cystic Ovarian Syndrome (PCOS) tend to have higher rates of infertility and miscarriage.  Some research suggests that a past history of multiple miscarriages may increase the risk of miscarriage after an amniocentesis.  So the question remains, do women of size with PCOS have a higher risk for miscarriage after an amniocentesis?  If so, is it because of their size, their history of infertility, or their history of miscarriages?  These questions remain unanswered at this time.  

Because amniocentesis is more difficult in larger women and may be somewhat more risky, large women should carefully consider the possible pros and cons before deciding whether or not to have this procedure done.  It may be that because it amnios may be somewhat more risky in obese women, larger women should think twice before having one done.  

On the other hand, if you strongly desire an amnio, size should not preclude you from having one.  It may make for a somewhat more challenging procedure, but many obese women have had amnios without problems, so certainly size should not be the only issue you consider in making your choice.  If you were of average size and would definitely choose an amnio, obesity should not keep you from choosing it either. Chances are excellent that everything would go fine. 

Amniocentesis: Not A Required Test Because of Size

Because larger women are at increased risk for certain types of birth defects, they often face great pressure to have prenatal testing procedures like AFP tests and amnios done. The value of these tests, however, is debatable.  

While women of size are at somewhat increased risk for Neural Tube Defects (NTDs) and certain developmental defects (like facial clefts or heart defects), the risk is not extreme, merely modestly increased.  Large women are not at increased risk for genetic defects.  Therefore, increased pressure to have an amnio (which works best to detect genetic or chromosomal defects) simply because of size makes no sense.  

Amniotic fluid taken during an amnio can be tested for AFP levels (to check for NTDs). It is unknown but possible that amniotic fluid AFP tests might be slightly more accurate than blood serum AFP tests in obese women, although no data is available to confirm this.  Since larger women have higher blood plasma volumes, research has noted that this "dilution" effect can result in higher rates of 'false positive' AFP serum tests. Presumably amniotic fluid levels would not have this same dilution effect in bigger women, and the results might be less subject to 'false positives.'  

However, at this time, this is pure speculation, and Kmom is aware of no data testing this possibility. Furthermore, a number of recent studies suggest that amnio AFP testing is outdated and no longer useful. Therefore, doing an amnio because it might offer a more accurate AFP result in obese women is probably not a reasonable justification for the test, especially given the miscarriage risk accompanying amnios.

The bottom line is that maternal blood serum testing is still more advantageous than amnio AFP testing because it offers no risk to the baby.  Amniocentesis is associated with about a 0.5%-1.0% increase in miscarriage risk, not to mention the increased risk of uterine infection for the mother.  Therefore, while it is unclear what the most accurate mode of testing for NTDs in obese women, at this time blood serum testing is still the more desirable test because it offers the least risk to the baby and mother. 

However, that doesn't mean that all obese women should be doing serum AFP testing either, as there are significant other problems associated with this test as well, including a high rate of 'false positives' in women of size.   It simply means that if a large mother strongly wishes to opt for prenatal testing for birth defects like NTDs, the maternal serum AFP/Multiple Screen probably involves less risk than amniocentesis.  

There are significant risks as well as benefits to ANY prenatal test, and women must weigh carefully the benefits and risks of any test they choose, or whether to skip prenatal testing completely.  Obesity does NOT mean that prenatal testing is required. On the contrary, because of higher rates of 'false positives,' it means that big women must research the issue even more carefully before they make their choices.  They should be aware that they may be more at risk for "false positives" and increased (and risky) invasive testing as a consequence of early prenatal testing like AFP/Triple Screens and ultrasounds.  

Ideas to Consider If You Do Choose An Amnio

If you do choose to have an amniocentesis, rest assured that many large women (including 'supersized' women) have had the procedure done without problems.  Your size does not mean that there will be problems, just that it is more technically difficult to perform.  Many women of very significant size have had amnios done without problems, so don't spend too much time worrying about your size if you do choose to have an amnio. Worry more about finding the right doctor to do the procedure, which is probably a more significant factor.

For women who are truly supersized or who have very significant abdominal adiposity, it has been suggested that a longer needle may be helpful in doing the amnio.  Kmom has heard conflicting information about whether a longer amniocentesis needle is available, but it probably is. If you plan to have an amniocentesis, ask your doctor beforehand about the possibility of using a longer amniocentesis needle, especially if you are supersized or have very significant abdominal adiposity.   Be sure to mention on the phone when making the appointment that you are a large-sized woman, and inquire whether a longer amnio needle is available at that facility. 

If you really want an amnio, it is probably a good idea to go to a tertiary center that specializes in prenatal diagnosis to have your amnio instead of doing it with your local doctor.  Research shows that miscarriage rates after amnios are lowest in tertiary centers that specialize in prenatal diagnosis.  No data exists on whether that is also true for obese women, but it certainly seems logical that going to a prenatal diagnosis specialist might be especially important for women of size. They would probably also be more likely to carry specialized equipment like longer amnio needles.

Wherever you have an amnio, you might also want to specifically request a doctor who has a lot of experience doing amnios in larger women as well.  Because amnios in larger women can be technically more difficult, you want to find a doctor who is experienced in that situation, knows when a longer needle may be needed, and how best to accomplish the amnio under more challenging circumstances.   You also want one who is not fat-phobic and won't blame any and all problems on your size.  

When to do the amnio is another debate for women of size.  Amnios can be done in the second trimester anywhere from 13-20 weeks, but amnios at 13-14 weeks are associated with higher rates of problems in women in some studies.  Therefore, as a woman of size whose amnio may be harder anyhow, you probably want to avoid an amnio early in the second trimester.  

Amnios are most commonly done at about 15-16 weeks.  Anecdotally, some supersized women have found that waiting a bit longer makes it more likely that a successful "tap" will occur on the first try. How long to wait is open to debate, though. If you would consider terminating a pregnancy based on amnio results you might not want to wait long, as later abortions are much harder physically and are more dangerous as well. In addition, a few studies have showed an increased rate of fetal loss in amnios beyond 19 weeks, although this data is debatable.  

Therefore, although the evidence is only anecdotal at this point, it may be optimal for heavy women to do an amniocentesis at about 17-18 weeks.  It must be emphasized that no data is available to confirm or disprove this, but it does seem to be something that big moms are told sometimes when considering an amnio.  

Because amnios are harder to do in women of size, there may be an increased risk for multiple needle insertions.  This is associated with an increased risk for fetal loss in some studies.  Therefore, you may wish to discontinue an amnio if more than 2 needle 'sticks' are required, or you may even choose to discontinue an amnio if the first 'stick' is not successful.  You may choose to return at another time for a separate amnio, or you may choose to discontinue the amnio altogether.  It's up to you.

If you know you plan to have an amnio, you should ask your health provider's opinion about the timing of amniocentesis in larger women before scheduling your procedure.  Don't forget to also ask about whether a larger needle might be needed and whether one is available at that facility, and discuss your wishes about the number of needle insertions you are comfortable with.


In conclusion, although some resources suggest that obesity increases the risks associated with amniocentesis, it is difficult to find research literature that discusses these allegations in detail.  

One study strongly suggests that increasing BMI is associated with a higher rate of fetal loss after Early Amniocentesis, but does not say whether this is true in second-trimester amnios.  Because Early Amniocentesis is riskier and rarely performed anymore, this study is of limited value in understanding miscarriage risks for women of size with later amnios.  It suggests there may be an increased risk, but more research is needed.

Because fetal loss may be increased in women of size during second-trimester amniocentesis too, big moms may want to think twice about having an amnio.  However, the risk for fetal loss is probably not that high either way, so if you truly want an amnio and are well-read about the possible risks, it certainly is a reasonable choice to make. 

It is clear that abdominal obesity does make performing amniocentesis more challenging technically, and that may lead to a higher rate of "missed" or difficult taps.  Even so, though, most obese women have very normal amniocentesis experiences with no major difficulties.  It may help to choose a major tertiary care center that specializes in prenatal diagnosis, and to ask for an amnio doctor that is size-friendly and very experienced in doing amnios on larger women.

Very heavy women may sometimes need a longer amniocentesis needle, and sometimes delaying the amnio for a couple of weeks makes it go easier.  If you are sure you will choose to have an amnio, call your amnio doctor before your appointment and discuss these issues over the phone.  

In addition, if you are sure you are going to have an amnio, be sure to go over the Amniocentesis Hints found on the main amniocentesis FAQ on this website.  


Large Moms' Stories of Amniocentesis

GAMom's Story: We had our first round of tests and it came back with levels increased. Our doctor informed us that it was probably just a false positive but sent us to a perinatologist anyway...Two amnios were attempted but the needle wasn't long enough. And MAN, did they hurt!!!! They monitored closely and took precise measurements to ensure the baby was okay. 

Sal's Story: After 16 weeks of bedrest my OB recommended that we induce at 36 weeks if an amniocentesis showed mature lungs.  The night before the amnio we were preparing for the baby and I fell down the stairs (14 steps), fracturing my spine in 3 places, breaking my tailbone, and injuring my shoulder. The injuries were evaluated and found to be stable and not in need of surgery (thank goodness!).  The amnio was performed and my doctor missed on the first attempt, had success on the second attempt, and the lungs were immature.  However, the amnio triggered contractions so I had to spend a day in L&D.  My blood pressure skyrocketed [and we decided to do an] induction at 37 weeks.  

Isadora E's Story:  I did have an amnio (actually, because my husband wanted it; I would have skipped it).  I was pretty frightened about the procedure.  But it was painless and went very quickly.  It also told us that our baby had none of the problems they test for.  

Sarah's Story:  [paraphrased from several emails she sent]  I [was] almost 20 weeks and was going through a lot of trouble with my OB around the AFP screening.  I'd taken the test twice, had "abnormal" results both times (1/110 chance), but had two ultrasounds that showed no problems.  My doctor [began] pushing hard for an amniocentesis and, regardless of the results, thinks I should be monitored as a high risk pregnancy, all based on a highly unreliable screening test.  I am very frightened about all this, and feel like my pregnancy, an event that was once just "mine," is now being taken over by doctors and machines and more and more tests.  

[Eventually], I decided to have the amnio...It was a hard decision to make.  I really didn't want to put this baby, who I instinctively felt was fine, at risk.  But I also didn't want to spend the rest of my pregnancy worrying about what might possibly be wrong.  I spoke with a friendly midwife and she really brought it home for me.  She said I should think about what I'd get out of having the amnio.  What result would change my thinking and why?  How would I feel about results either way?  

I realized that knowing "for sure" would make me feel a lot better.  I could stop thinking about my high AFP levels every time I thought about the baby.  What clinched it was a letter I wrote to the baby.  I've been writing to him my whole pregnancy, telling him all the different things that have been happening and all my thoughts on being unexpectedly pregnant, and when I started telling him about the abnormal test results and the ongoing struggle, I realized that my constant state of low-level worry and stress was probably affecting him too, and that I didn't want him to spend the rest of his pre-birth feeling those feelings.  Maybe it seems silly, I know he can't comprehend my emotions, but I'm sure that my emotions are producing physical responses in my body that he does experience, even if he only recognizes them as the slightly uncomfortable tension of my stress.

So I decided to have the amnio.  Even though I cried through the whole thing it was actually not a terrible experience.  I was glad when it was over and wouldn't do it again, but the pain was less than I expected and it was interesting to feel the needle poke through the flesh of my belly and then into my uterus.  I was surprised to be able to feel the moment that happened.  

Afterwards...I felt some regret about having the procedure done, especially after reading how the triple screen may not be [as] valid for women who weigh over 250 lbs.  I felt (and still feel) very angry that not one of the ten or so health care providers I've seen since I received my initial triple screen result mentioned this possibility.  They put me and my baby at risk because they choose to be ignorant about health care issues for fat women.  

Now that I've gotten my amnio results and learned that the baby is "perfectly normal" (doctor's words), it seems very likely that my triple screen results were more a result of my weight than any sort of actual issue.  All that worry, all that stress, worrying my family and friends, and even a procedure that could have caused a miscarriage, because I happen to be fat in a medical system that considers one model, a thin one.  

Although I wish I had never taken the triple screen to begin with, I'm glad I had the amnio to resolve my doubts. "Knowing" that the baby is okay has relieved my mind so much!  I finally feel good about my pregnancy again.  I feel like all that doctor stuff was just a bad dream.

Needless to say, I'm in the process of switching my care to the midwife I've been consulting during this whole process.  She's much more hesitant about traditional medical intervention and I think she's going to be great at helping me take back control of my pregnancy.  I really worry about other fat women, though. I'm lucky because I have the time and resources to question everything and to work hard to find answers.  So many other women don't think to question something so authoritative as the medical establishment.  Doctors are always right, right?

Kmom's Story: My own experience with amniocentesis was an unpleasant one, so I tend to be cautious about them. I would not do one again, frankly, except under the most pressing circumstances. 

I had one with my first pregnancy, due to a low AFP test result. They told me my baby might have Down Syndrome.  Because I have no family medical history available to me, this possibility was especially frightening to me.  I didn't feel I had a choice about having the amnio; the doctors pretty much just assumed I'd have one and pressured me into one.  Although I was scared, I felt at the time that I should probably do one, just to "know for sure" what was going on with the baby.  

But at night the idea that there might really be a problem with the baby was agonizing.  Every member of our families felt that if the baby had Down Syndrome, abortion was the only option.  I alone felt that I could not consider abortion when I was already feeling the baby move, when the baby had already become "real" to me and bonded with me.  It was an incredibly stressful time. 

Before the amnio, we saw a genetic counselor. He drew up a chart of our family histories, which showed no problems on my husband's side and a depressingly blank slate on my side.  Still, he was very encouraging and nice and reassured us that my risk was low, despite my lack of family history. 

We did a level 2 ultrasound, which found that the baby might be younger than thought and that might be the reason behind the "low" AFP test we experienced.  He gave us the choice of opting out of the amnio, since a different dating based on my longer menstrual cycle significantly reduced my "odds" ratio of Down's.  Although that was tempting (and I wish I'd walked out now!), realistically there was no way I could have been at peace with "not knowing for sure" what was going on with the baby.  That's the slippery slope of prenatal testing; once you start down it, it's very difficult to pull back or get off.  You keep getting pushed into more and more invasive stuff, either by people around you or by your own anxiety and "need to know."   

The amnio started out fine; I felt the needle pierce the uterus but it was basically like a moderate cramp---not a big deal. However, my daughter was very active that day and they had to withdraw the needle, reposition it, and try again due to her position changes. This time, my uterus became very hard (probably a Braxton-Hicks contraction) and the doctor had difficulty getting the needle in. Once it was finally in, he had a hard time getting it in enough to withdraw a sufficient amount of fluid. He put a tremendous amount of pressure on me and it was extremely uncomfortable, even painful.  The atmosphere in the room became very tense, and the procedure really hurt the second time.  This is not an experience I ever care to repeat. He finally got enough fluid to make the test possible, but only barely. I lived in terror of having to repeat the test. 

I also experienced cramping and bleeding a couple of days after the test (after doing some heavy lifting I shouldn't have done), and was scared to death that the baby would be 'normal' but I would miscarry anyway. What I didn't know is that early pregnancy bleeding (I had had spotting all through the first trimester) may make a miscarriage after amnio more likely.  If I had known that, I might well not have chosen to take the test---but no one bothered to inform me of this important fact.  Fortunately, everything turned out fine, but it was a scary couple of days.

After the amnio, the doctor mentioned briefly the uterus contraction but mostly blamed my abdominal fat for his difficulties.  While my abdomen is ample, it's not really huge and I know women with much larger bellies than mine who had easy amnios, so I doubt my belly was the main source of difficulty. Still, I felt terribly guilty and I left the appointment in tears, absolutely devastated about my size and the difficulties it supposedly caused.

Not being a doctor, I cannot say for sure what the problem was, but I think now that while the adiposity didn't help, the uterine contractions were probably more of a factor, since the first try was not difficult at all. If the issue had really been adiposity, the first try would have also been difficult and it was not.  I think it was the contraction that caused the problem, and I wonder why he didn't wait for the contraction to subside instead of trying to force the issue. But instead, he simply blamed the problem on my size, and pretty brutally, I might add.  I was really emotionally devastated by the way he lectured me afterwards.

I have strong doubts that my size really was the real problem. Many health practitioners are very quick to blame any problems on adiposity, and to be fair, sometimes it is a factor. However, sometimes it is not, and a doctor's personal technique makes a lot of difference, so you never know. After much reflection, I feel that he was unfair in blaming my size for the problem, and he certainly should not have been so unkind and judgmental about it to me. 

Although I am not usually shy about confronting size-phobia, I was so emotionally vulnerable from worry and guilt over a possible birth defect and the tremendous difficulty of the amnio that I meekly accepted his condemnation and left in tears. In later weeks, I agonized over the experience.  Even more tellingly, it created a lasting sense of body betrayal, worry over my size and how it was "messing up things," and lack of trust in my own body's ability to gestate and "do" things properly.  It was part of the chain of demoralizing events that sapped my confidence in myself and my body as a large woman, and ultimately led to a horrific birth experience a few months later.

In retrospect, I think he should have used a different-sized needle and waited for the contraction to subside before forcing the issue. We'll never know for sure if this would have helped, but I do think that it's a good possibility the whole situation was mishandled. Certainly he should never have been so judgmental about my size.

As noted, other fat women (including some 'supersized' ones) on the BigMoms and OPSS mailing lists have had amnios with no problem, so don't assume your fat will be a problem if you choose to have an amnio. Just be sure that the amnio is really necessary before undertaking one, discuss whether the doctor has had experience doing amnios on large women, and ask whether a longer needle and/or a delay in the test is advisable. 

The key is to be assertive about demanding size-friendly care; whatever you do, don't feel guilty, apologize for your size, or meekly accept poor treatment just because you are larger than their average patient.  If needed, take along an "advocate" for you, to help you speak about your concerns during the consultations or procedure.  It's usually best if this is someone besides your husband/partner; it helps if it is someone who is not emotionally involved with the baby or deeply invested in the outcome.  They are then more objective in their listening and questioning and can take notes for you during your consultation.  

Large women deserve respectful treatment with appropriate equipment and technique adjusted for our size as necessary. It is the duty of the amnio doctor to be ready for the needs of a wide variety of women. Adiposity can make amnios more challenging to perform, but it is the duty of the doctor to be prepared to treat ALL women, regardless of circumstance. And no woman should be chastised or treated disrespectfully, no matter what "challenges" are encountered.  Demand excellent treatment, whatever you choose to do.  ---------------------Kmom




A Guide to Effective Care in Pregnancy and Childbirth.  Enkin, M., Keirse, M., Renfrew, M. & Neilson, J.  3rd edition. Oxford: Oxford University Press.  2000. --------------

Superb review of childbirth issues and management controversies.  Extremely evidence-based, very fair and clear.  Highly recommended.

The Tentative Pregnancy: How Amniocentesis Changes the Experience of Motherhood.  Barbara Katz Rothman.  New York: W. W. Norton & Company, 1993.  Available from or or

An excellent overview of the debate over prenatal testing of all kinds, but especially amnios.  Represents multiple points of view fairly.  Author interviewed a number of genetic counselors, doctors and other health professionals, as well as parents who had been through prenatal testing.  Shares the stories of families who chose testing, who received reassuring and non-reassuring results, and the choices that they made.  Not an easy book to read but certainly one that anyone dealing with prenatal testing should read.

Precious Lives, Painful Choices: A Prenatal Decision-Making Guide.  Sherokee Ilse.  Maple Plain, Minnesota: Wintergreen Press, 1995.  Available from

An excellent resource for parents who have received non-reassuring test results and now face difficult choices about what to do next.  Written with great compassion and understanding.

Websites About Amniocentesis

General Websites About Prenatal Testing

Websites About Clubfoot (Talipes)

Websites and Resources About Down Syndrome

News Stories About Amniocentesis


Medical Journal Articles About Amniocentesis

General Information About Amnios

Tabor, A et al.  Randomised controlled trial of genetic amniocentesis in 4606 low-risk women. Lancet. June 7, 1986. 1(8493):1287-93.

Randomized, controlled trial of 4606 women without known risk of genetic disease (ages 25-34 years).  Spontaneous miscarriage risk was 1.7% in the amnio group and 0.7% in the control group (no amnio, only an ultrasound).  Risk factors for miscarriage included increased AFP levels before amnio, perforation of the placenta during amnio, and withdrawal of discolored amniotic fluid.  There was more amniotic fluid leakage in the amnio group afterwards but no more vaginal bleeding. Rate of postural malformations was the same in the 2 groups.  However, "Respiratory distress syndrome was diagnosed more often (relative risk 2.1) and more babies were treated for pneumonia (relative risk 2.5)." 

Morrow, RJ et al. Ultrasound detection of neural tube defects in patients with elevated maternal serum AFP tests.  Obstet Gynecol.  1991. 78:1055-7. [from abstract]

Found that high levels on the AFP maternal serum test were associated with an increased risk for miscarriage after amniocentesis.  A targeted ultrasound may be the better first choice to check for NTDs after a high AFP test.

Anandakumar, C et al. Amniocentesis and its complications. Aust N Z J Obstet Gynaecol.  May 1992.  32(2):97-9.

Study from Singapore designed to test whether an experienced operator influenced the incidence of complications with amniocentesis. Complications like fetal loss, blood-stained amniotic fluid, culture failure, multiple needle puncture, leaking amniotic fluid, fetal trauma, and error was less common in the group with more experienced operators. 

Baird, PA et al. Population-based study of long-term outcomes after amniocentesis. Lancet. Oct 22, 1994.  344(8930):1134-6.  

Studied 1296 cases where women has amniocentesis, and 3704 controls where amniocentesis was not used.  Followed up cases and controls for 7-18 years.  The offspring of women who had had amnios were NO more likely to experience hearing problems, learning difficulties, visual problems, or limb anomalies than those who had not experienced amniocentesis.  The one exception was a higher rate of hemolytic disease due to ABO isoimmunization.  

Gillberg, C et al.  Long-term follow-up of children born after amniocentesis. Clin Genet.  January 1982.  21(1):69-73.  

122 children were followed, 62 of whom had been exposed to amniocentesis in utero.  They were examined between 5-7 years of age.  No differences were found between pediatric or neurodevelopmental disorders, orthopedic abnormalities, or respiratory problems during the neonatal period. 

Sant-Cassia, LJ et al. Midtrimester amniocentesis: is it safe?  A single centre controlled prospective study of 517 consecutive amniocenteses.  Br J Obstet Gynaecol.  Aug 1984.  91(8):736-44.

517 consecutive patients having an amnio in one center were followed.  289 of these were compared with 289 matching controls with no amnios.  There was no significant difference in rates of fetal loss, perinatal mortality or vaginal bleeding between groups.  There was however an increased risk for preterm delivery.

Abboud, P et al. Amniotic fluid leakage and premature rupture of membranes after amniocentesis.  A review of the literature.  J Gynecol Obstet Biol Reprod (Paris).  December 2000.  29(8):741-745.

Reviews the medical literature on the rare complication of amniotic fluid leakage and premature rupture of membranes.  In 13 recent studies, found 280 cases of amniotic fluid leakage in 17, 186 amnios.  Risk was increased with early amnio (<15 weeks) and when the needle was inserted far from the placenta.  Noted that bedrest "gave good results."  However, "Significant loss of amniotic fluid compromises pregnancy...When amniotic leakage persists for more than two weeks, there is little spontaneous resolution.  The risk of pursuing the pregnancy should be discussed with the couple in this case.  Risks include respiratory disorders, skeletal malformations and premature birth. New techniques such as 'amniopatch' may play an important role in the near future."  

Finnegan, JA.  Amniotic fluid and midtrimester amniocentesis: a review.  Br J Obstet Gynaecol.  Aug 1984. 91(8):745-50.

"A review of experimental amniocentesis in animals suggests risks to limbs and structural changes in fetal lungs.  In humans, orthopaedic abnormalities and respiratory difficulties appear to be a risk of amniocentesis, and studies addressing these risks are also reviewed.  Continued investigation of risks from fluid loss at midtrimester amniocentesis is recommended."

Finegan, JA et al. Infant outcome following mid-trimester amniocentesis: developmental and physical status at age six months. Br J Obstet Gynaecol.  Oct 1985.  92(10):1015-23.  

91 infants whose mothers had had amnios were compared with 53 infants whose mothers chose not to have amnios.  "The results indicated that amniocentesis does not appear to influence infant mental and motor development, temperament, physical growth, or the risk of orthopaedic abnormalities.  However, amniocentesis is not entirely free of risk because several of the infants had needle marks."  

Finegan, JA et al.  Child outcome following mid-trimester amniocentesis: development, behavior, and physical status at age 4 years. Br J Obstet Gynaecol.  Jan 1990.  97(1):32-40.

88 children whose mothers had had amnios were compared with 46 children whose mothers did not have amnios.  "The results suggest a wide range of developmental and behavioral variables studied is not influenced by removal of amniotic fluid in the mid-trimester. However, mothers who had amniocentesis were more likely to report a history of ear infections in their child...In support of this finding were the results of audiological assessment which demonstrated a trend toward a higher rate of bilateral middle-ear impedance abnormalities in children whose mothers had amniocentesis...Further study of the upper respiratory system is recommended to explore potential long-term sequelae of mid-trimester amniocentesis."

Finegan, JA et al.  Children whose mothers had second trimester amniocentesis: follow-up at school age. Br J Obstet Gynaecol.  March 1996.  103(3):214-8.

Same sample of children (86 exposed to amnios, and 44 controls this time) were examined at school age. No differences between groups were found.  "Second trimester amniocentesis does not appear to compromise child development, behaviour, growth or health."

Greenough, A et al. Invasive antenatal procedures and requirement for neonatal intensive care unit admission. European Journal of Paediatrics. 1997.  156: 550 - 52.

NICU admissions are increased in babies who have been exposed to amniocentesis. 

Amnios and Miscarriage

Papantoniou, NE et al. Risk factors predisposing to fetal loss following a second trimester amniocentesis.  BJOG.  October 2001.  108(10):1053-6.

Greek study that found that several factors seemed to be related to an increased rate of fetal loss following a second trimester amnio.  Women older than 40 years had about twice the fetal loss rate of younger women.  Women with a history of vaginal bleeding in the current pregnancy had 2.4x the risk for fetal loss.  Women with a prior history of 3+ first-trimester abortions or a second trimester miscarriage or abortion had an even higher risk for fetal loss (3.03x the risk).  

Ropwe, EC et al. Genetic amniocentesis: gestation-specific pregnancy outcome and comparison of outcome following early and traditional amniocentesis.  Prenatal Diagnosis.  Sept. 1999.  19(9):803-7.  

Found that miscarriage rates after amniocentesis varied significantly by week of gestation.  Found higher rates of fetal loss in amnios performed at or after 19 weeks of gestation. Also notes that miscarriage can occur as long as 6 weeks after the amnio.

Suggests that women not be quoted one single rate of risk for miscarriage, but rather a range of possible rates, based on weeks of gestation when amniocentesis is performed and including cumulative rates that include fetal loss that occurs even after several weeks have passed after the amnio. 

Saltvedt, S and Almstrom, H.  Fetal loss rate after second trimester amniocentesis at different gestational age.  Acta Obstet Gynecol Scand.  Jan 1999.  78(1):10-4.  

Swedish study that found that earlier amnios were associated with a higher fetal loss rate.  Amnios that were performed between 13-20 weeks were studied; the fetal loss rate was highest at 13 weeks.  One-third of losses occurred within 2 weeks of the amnio, and the rest were within 7 weeks of the amnio, so obviously losses can and do occur even once the immediate period after the amnio has passed.  Abnormal color of amniotic fluid and leakage of amniotic fluid were "strong predictors of fetal loss."  Tranplacental needle insertion, on the other hand, did not increase the risk for loss.  

Marthin, T et al. Transplacental needle passage and other risk-factors associated with second trimester amniocentesis.  Acta Obstet Gynecol Scand.  Sept. 1997.  76(8):728-32.

Followed all pregnancies that underwent midtrimester amniocentesis over a 10 year period in one Swedish medical center, and the risk factors for pregnancy loss associated with amnios.  2083 pregnancies were considered.  "There was a slight but nonsignificant relationship between the degree of experience of the gynecologist and risk for pregnancy loss.  A more experienced operator used significantly fewer needle insertions...Multiple needle insertions were also associated with a slight, albeit nonsignificant, increase in incidence in fetal loss (3.8% after 3 or more insertions vs. 1.2% after one insertion).  No difference in spontaneous abortion incidence was found in patients having an anterior versus a posterior placenta, nor did transplacental needle passage increase the risk for pregnancy loss."

Cruikshank, DP et al.  Midtrimester amniocentesis.  An analysis of 923 cases with neonatal follow-up.  American Journal of Obstetrics and Gynecology.  May 15, 1983.  146(2):204-11.  

Study on amnios from the 1980s that found the risk of spontaneous abortion as a result of amniocentesis varied from 0.2% to 1.4%.    Stained amniotic fluid was associated with a much higher risk for fetal loss (29%).  Unexplained elevations of AFP were associated with a 38% risk for a low birth weight infant.  "The only neonatal complication associated with amniocentesis was an apparent marked increase in the incidence of lower-extremity orthopedic abnormalities."  

Shapiro, LR et al.  Immediate and unexplained fetal death during mid-trimester amniocentesis.  Prenatal Diagnosis.  April-June 1983.  3(2):151-4.  

Discusses "immediate and unexplained fetal death" DURING amniocentesis.  Surveyed US programs and found 5 cases from 7524 at 4 centers, a rate of 0.06%.  A "neurogenic mechanism is postulated."

McGahan, JP et al.  Ultrasound needle guidance for amniocentesis in pregnancies with low amniotic fluid.  Journal of Reproductive Medicine.  July 1987.  32(7):513-6.  

Discusses the use of real-time ultrasonography in helping during difficult amniocentesis cases.  Case reports of 6 difficult amnios in the presence of reduced amniotic fluid were discussed.  3 cases of very low fluid (oligohydramnios) were discussed (all 3 later resulted in fetal death).  3 cases where decreased (but not severely low) amniotic fluid was accompanied by maternal obesity were also discussed (outcomes were fine and reassured doctors there was a normal pregnancy).  However, one has to wonder about the wisdom of withdrawing amniotic fluid when low amniotic fluid is already suspected, and whether that played a role in the 3 deaths from oligohydramnios.

Amnios and Respiratory Problems

Annapoorna, V et al.  Evaluation of auditory system in preschool children whose mothers had mid-second trimester amniocentesis.  J Perinat Med.  1996.  24(3):207-12.

Singapore study of 59 children exposed to midtrimester amniocentesis, and 63 control children.  There was no significant increase in NICU rates, impairment of speech, language development, or auditory function in children exposed to amnios.  However, incidentally, the authors found an increased incidence of respiratory illness in the amnio group (57.6%) compared with the control group (30.1%) and called for further study of this finding.

Milner, AD et al.  The effects of mid-trimester amniocentesis on lung function in the neonatal period.  Eur J Pediatr.  June 1992.  151(6):458-60.

39 healthy full-term babies who had been exposed to mid-trimester amniocentesis had lung function tests, as well as 42 controls.  "Babies subjected to amniocentesis had a significantly lower dynamic compliance...and tended to have higher resistance compared to controls...This provides further evidence that mid-trimester amniocentesis does have an adverse effect on lung growth and development."

Hunter, AG.  Neonatal lung function following mid-trimester amniocentesis.  Prenatal Diagnosis.  July 1987.  7(6):433-41.

354 women who had midtrimester amniocentesis were matched with controls who did not have amniocentesis, in order to compare the neonatal respiratory status of their offspring.  "There was no evidence that the infants exposed to genetic amniocentesis were compromised."

Early Amniocentesis

CEMAT Group.  Randomised trial to assess safety and fetal outcome of early and midtrimester amniocentesis.  The Canadian Early and Mid-trimester Amniocentesis Trial (CEMAT) Group.   Lancet.  Jan. 24, 1998.  351(9098):242-7.  

*The* big study on early amniocentesis vs. second trimester amniocentesis.  Women were randomly allocated to early amniocentesis (11-12 weeks) or midtrimester amniocentesis (15-16 weeks).  11 mL of amniotic fluid were removed in EA and 20 mL in MA.  No more than 2 needle insertions were done on the same day.  Maternal and fetal health were assessed at 20-22 weeks and again 5 weeks after delivery.  

There were more losses in the EA group (7.6% vs. 5.9%), and significantly more clubfoot (1.3% vs. 0.1%).  There was more post-amnio fluid leakage in the EA group (3.5% vs. 1.7%).  "Our study shows that early amniocentesis is associated with an increased risk of fetal loss and talipes equinovarus [clubfoot]." 

Johnson, JM et al.  Technical factors in early amniocentesis predict adverse outcome.  Results of the Canadian early (EA) versus mid-trimester (MA) amniocentesis trial.  Prenatal Diagnosis.  August 1999.  19(8):732-8.  

Examined Early Amniocentesis vs. Midtrimester Amniocentesis.  Found a number of factors associated with higher fetal loss during EA, including increased Body Mass Index, higher parity, 'difficult' procedures, post-procedure amniotic fluid leakage, bleeding, maternal hypertension, etc.  

Early Amnios were associated with higher rates of fetal loss, clubfoot, failed procedures, multiple needle insertions, amniotic fluid leakage, and failed cultures. "Performing amniocentesis before 13 weeks gestation (EA) was the major predictive factor for adverse outcome.  These data suggest that first-trimester chorionic villus sampling (CVS) and MA will likely remain the invasive procedures of choice for evaluation of fetal karyotype."  Also found a higher rate of problems in amnios at 14 weeks, even though that may not be technically considered Early Amniocentesis by many resources.

Thompson, PG et al.  Lung volume measured by functional residual capacity in infants following first trimester amniocentesis or chorion villus sampling.  Br J Obstet Gynaecol.  June 1992.  99(6):479-82.

Compared the incidence of respiratory problems and lung volume abnormalities  in babies who had had first-trimester amnios (n=74) or chorionic villus sampling (n=86).  Used measurements of "functional residual capacity." CVS was associated with a higher incidence of neonatal respiratory distress (7%) vs. early amniocentesis (0%).  However, both groups showed high rates of low functional residual capacity.  "Both amniocentesis and CVS performed in the first trimester of pregnancy may impair antenatal lung growth."

Yuksel, B et al. Perinatal lung function and invasive antenatal procedures. Thorax.  Feb 1997.  52(2):181-4.

Notes that second trimester amniocentesis has been associated with "an excess of perinatal lung function abnormalities."  Examined first trimester amnios and first trimester CVS.  Found that "Procedures performed in the first trimester were independently associated with a high airways resistance.  These results suggest that invasive procedures performed in the first trimester of pregnancy have an adverse effect on perinatal lung function."

Greenough, A et al.  First trimester invasive procedures: effects on symptom status and lung volume in very young children. Pediatr Pulmonol.  Dec 1997.  24(6):415-22.

Assessed the impact of first trimester CVS and Early Amniocentesis on respiratory morbidity in young children (1 year).  Functional Residual Capacity was also measured in 5 month old babies who were exposed to CVS or EA prenatally (and also in controls).  Found an excess of respiratory symptoms and chest-related hospital admissions in the EA group compared to the controls. Positive symptom status was related significantly to EA and CVS interventions, bottle feeding, parental smoking, family history of atopy (allergies), and immaturity.  "We conclude that first trimester procedures are associated with increased respiratory morbidity in very young children."

Tharmaratnam, S et al. Early amniocentesis: effect of removing a reduced volume of amniotic fluid on pregnancy outcome.  Prenatal Diagnosis.  Aug 1998.  18(8):773-8.

Discusses the theory that removing less fluid (about half of that removed during second trimester amnios) during early amniocentesis might help improve prognosis.  Suggests that fluid depletion from amnios may persist for 7-10 days, a significant departure from what most amnio literature says. By removing 7 ml they obtained a 3.8% miscarriage rate, a 2.7% respiratory difficulty rate at birth, and a 1.6% rate of "fixed flexion deformities," all at the price of a small increase in the incidence of culture failure (2.2%).   

Nikkila, A et al. Early amniocentesis and congenital foot deformities. Fetal Diagn Ther.  May-June 2002.  17(3):129-32.  

This study examined the rate of foot deformities after amnios done at 12-14 weeks; other studies have examined the rate of foot deformities in early amnios done before 13 completed gestational weeks.  Found a higher rate of foot deformities than they expected (odds ratio 1.74).  The rate of spontaneous miscarriages after the amnio was 1.8% and the rate of amniotic fluid leakage was 1.9%.  "There was a significant trend for all complications to decrease with increasing gestational age at amniocentesis."

Amniocentesis and Obesity

Johnson, JM et al.  Technical factors in early amniocentesis predict adverse outcome.  Results of the Canadian early (EA) versus mid-trimester (MA) amniocentesis trial.  Prenatal Diagnosis.  August 1999.  19(8):732-8.  

Examined Early Amniocentesis vs. Midtrimester Amniocentesis.  Found a number of factors associated with higher fetal loss during EA, including increased Body Mass Index, higher parity, 'difficult' procedures, post-procedure amniotic fluid leakage, bleeding, maternal hypertension, etc.  

Early Amnios were associated with higher rates of fetal loss, clubfoot, failed procedures, multiple needle insertions, amniotic fluid leakage, and failed cultures. "Performing amniocentesis before 13 weeks gestation (EA) was the major predictive factor for adverse outcome.  These data suggest that first-trimester chorionic villus sampling (CVS) and MA will likely remain the invasive procedures of choice for evaluation of fetal karyotype."  Also found a higher rate of problems in amnios at 14 weeks, even though that may not be technically considered Early Amniocentesis by many resources.

Regarding obesity and EA, "Maternal factors found to be independently predictive of fetal loss included increased BMI...Increased BMI was also a predictive factor for a 'difficult procedure', which in turn was associated with an increased risk of fetal loss.  This implies that maternal obesity likely imposes technical challenges to the operator, increasing the probability of a difficult procedure and of post-procedure complications."

Because there was limited fetal losses in the later amnio group (MA), any potential association between obesity and fetal loss in the traditional form of amniocentesis was unable to be investigated.  

McGahan, JP et al.  Ultrasound needle guidance for amniocentesis in pregnancies with low amniotic fluid.  Journal of Reproductive Medicine.  July 1987.  32(7):513-6.  

Discusses the use of real-time ultrasonography in helping during difficult amniocentesis cases.  Case reports of 6 difficult amnios in the presence of reduced amniotic fluid were discussed.  3 cases of very low fluid (oligohydramnios) were discussed (all 3 later resulted in fetal death).  3 cases where decreased (but not severely low) amniotic fluid was accompanied by maternal obesity were also discussed (outcomes were fine and reassured doctors there was a normal pregnancy).  However, one has to wonder about the wisdom of withdrawing amniotic fluid when low amniotic fluid is already suspected, and whether that played a role in the 3 deaths from oligohydramnios.

Amniocentesis and Rh Sensitization

Hill, LM et al.  Rh sensitization after genetic amniocentesis.  Obstet Gynecol.  Oct 1980.  56(4):459-61.  

Early study of the problem of Rh sensitiation in Rh negative women.  78 Rh negative women who had amnios without receiving Rhogam were studied.  56 were at risk for sensitization.  3 (5.4%) were sensitized, but this was not significantly higher than the 2.1% rate of spontaneous Rh sensitization during pregnancy.  However, a trend towards increasing sensitization after amnio was noted.  Authors recommend use of Rhogam in Rh negative women undergoing amniocentesis.  

Amniocentesis and Fetal Damage

Bruce, S et al. Skin dimpling associated with midtrimester amniocentesis.  Pediatr Dermatol.  Oct. 1984. 2(2):140-2.  

"Multiple dimple-like scars occurred in an infant whose mother had undergone midtrimester amniocentesis."  The authors then discuss the prevalence and diagnosis of this situation.  Note that this is a case study, and that this probably occurred at a time when continuous ultrasound monitoring was likely not being done with amnios.  

Therkelsen, AJ and Rehder, H.  Intestinal atresia caused by second trimester amniocentesis.  Case report. Br J Obstet Gynaecol.  May 1981.  88(5):559-62.  

Horrifying case report, not for the squeamish.  This was from the days when continuous ultrasound was not used and would be unlikely to occur now, but is still a sobering reminder of the potential risks of amnios.  In a mid-trimester amnio, a string of fetal mucosa and submucosa from the fetus' small intestine was found.  The implication is that this was diagnosed as a possible abdominal defect.  The baby was aborted 21 days later.  "There was no lesion of the abdominal wall" but they did find probable signs of fetal damage from the amnio.  In other words, the needle probably hit the baby and perforated its abdomen, damaging it and putting intestinal mucosa into the amniotic fluid that was withdrawn.  The baby was aborted within 3 weeks, but no birth defect was found, only probable damage from the amnio.   

Cross, HE and Maumenee, AE.  Ocular trauma during amniocentesis. Arch Ophthalmol.  Oct 1973. 90(4):303-4.

No abstract is given with this case report, but there are a few case reports of eye damage to the fetus from amniocentesis.

Young, PE et al.  Fetal exsanguination and other vascular injuries from midtrimester genetic amniocentesis.  Am J Obstet Gynecol.  Sept. 1, 1977. 129(1):21-4.  

Case report of fetal exsanguination (the baby bled out and died) after a midtrimester amniocentesis.  Examined 242 consecutive amnios and the results suggested that "fetal hemorrhage is relatively common and difficult to avoid during this procedure."  Suggests that fetal hemorrhage may be more common when the placenta is anterior.

Epley, SL et al.  Fetal injury with midtrimester diagnostic amniocentesis.  Obstet Gynecol.  Jan 1979.  53(1):77-80.

Examined 107 infants born after midtrimester amniocentesis.  "The frequency of fetal injury was 9%, and was directly related to the number of attempts at amniocentesis.  All were minor cutaneous injuries except for 1 case of disruption of a patellar tendon." Made suggestions for reducing the incidence of "fetal puncture."  [Note that this study was done before continuous ultrasound was used during most amniocentesis procedures.]

Karp, LE and Hayden, PW.  Fetal puncture during midtrimester amniocentesis. Obstet Gynecol.  Jan 1977.  49(1):115-7.  

4 cases of fetal puncture during second trimester amniocentesis were reported in this study. In one cases, the baby "apparently sustained temporary neurologic damage."  The authors reviewed their own data and the research literature and concluded that fetal puncture occurs in 1-3% of midtrimester amniotic taps.  "We conclude that midtrimester amniocentesis should not be considered a routine benign procedure; and whenever the use of this diagnostic modality is being considered, the prospective parents should be informed of its hazards."  [Again, this study was done before continuous ultrasound was used with amnios.]

Strauss, A et al. Intra-uterine fetal demise caused by amniotic band syndrome after standard amniocentesis.  Fetal Diagn Ther.  Jan-Feb 2000.  15(1):4-7.

Presents a case report of Amniotic Band Syndrome associated with second-trimester amniocentesis.   Amniotic Band Syndrome occurs when the inner sac of waters is disrupted or ruptures and "strings" of the sac go through the amniotic fluid.  Sometimes these "strings" go across parts of the baby and cause scars, restricted growth of the part affected, or even amputation of fetal limbs.  In this case, the amniotic band restricted the umbilical cord and the fetus eventually died. Although most cases of Amniotic Band Syndrome are not associated with amniocentesis, a few cases may be, and the authors caution that invasive prenatal testing like amniocentesis can induce rare complications like Amniotic Band Syndrome.  

Kohn, G. The amniotic band syndrome: a possible complication of amniocentesis. Prenatal Diagnosis.  May 1987.  7(4):303-5.  

Another case report of fetal damage.  "Malformations of the upper distal extremeties were noted in an otherwise healthy infant whose mother underwent diagnostic amniocentesis.  A causal relationship is postulated."  

Rehder, H.  Fetal limb deformities due to amniotic constrictions (a possible consequence of preceding amniocentesis).  Pathol Res Pract.  July 1978.  162(3):316-26.  

Discusses the amniotic band syndrome and 2 case reports of this.  One is thought to be associated with a prior amniocentesis.

The Debate Over The Best Invasive Prenatal Test

Jauniaux, E et al.  What invasive procedure to use in early pregnancy?  Baillieres Best Pract Res Clin Obstet Gynaecol.  August 2000.  14(4):651-62.

Discusses the pros and cons of the various invasive prenatal tests available.  "Mid-trimester amniocentesis remains the safest invasive procedure.  Chorionic Villus Sampling (CVS) and early amniocentesis (EA) are associated with a higher risk of subsequent pregnancy loss.  There is also a 10-fold increase in the risk of mosaicism with CVS compared to amniocentesis.  Both CVS and EA can induce fatal structural defects and should be abandoned as routine invasive tests.  Patient counselling should include an evaluation of the risk associated with each individual procedure but also the operator's personal complication rate."

Alfirevic, Z et al. Chorion villus sampling versus amniocentesis for prenatal diagnosis. Cochrane Database Syst Rev.  2000 (2):CD000055.

Compared randomized trials of CVS to second trimester amniocentesis.  CVS was associated with more "sampling and technical failures, and more false positive and false negative results." Pregnancy loss was more common after CVS (odds ratio 1.33).  There was also a suggestion, not statistically significant, that there was an increase in stillbirths and neonatal deaths after CVS.  The authors concluded, "The increase in miscarriages after chrion villus sampling compared to amniocentesis appear to be procedure related.  Second trimester amniocentesis appears to be safer than chorion villus sampling.  The benefits of early diagnosis with chorion villus sampling must be set against the greater risk of pregnancy loss."

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