by Kmom
Copyright © 1996-2000 Kmom@Vireday.Com. All rights reserved.
NOTE: It is not in the scope of this FAQ to truly cover prenatal testing thoroughly, only to address it as it concerns big moms. I urge all pregnant women to thoroughly research any test before deciding whether to use it or not. Do NOT accept blindly what your doctor tells you. Ask questions and consider all sides of the issue. Testing decisions vary greatly depending on family history, medical condition, parental beliefs, etc. For more information on prenatal testing, see the FAQs available from misc.kids.info on the Internet.
CONTENTS
"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 slightly 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 very 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 that "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 using 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 need to be sure they really understand what is being tested for, what the test measures and how accurate it is, the difference between a screening test and a diagnostic test, what it means if they get a non-reassuring screening test result, what their choices would be if they had a non-reassuring screening test result, what further testing might be available, what kind of possible treatment might be available if a condition did exist, whether this information before birth would be an advantage or disadvantage to them, and what they would do with the information once they got it. 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.
Ultrasounds use sound waves to help figure out what is going on inside the uterus. Most practitioners consider them safe, but there is a small vocal minority of critics that contend that their safety is unproven and so should be avoided whenever possible. It is probably a good idea to only use them when necessary, just in case. Most women in US society view ultrasounds favorably and would use any excuse to have multiple ultrasound exams. Certainly they are emotionally rewarding to see, and can be very reassuring. However, it's probably best not to overuse them unnecessarily. Although ultrasounds have never been proven conclusively to be harmful, neither have they been proven to be harmless either. They are simply a useful tool in some circumstances in pregnancy, but should not be abused through overuse since we have no proof of their lack of harm.
Reasons for doing an ultrasound vary greatly. Early in pregnancy, they may be used if an ectopic pregnancy is a possibility, to determine if the fetus has died, if twins are a possibility, etc. In the second trimester, it has become routine to do a more in-depth ultrasound to look for fetal abnormalities, multiple pregnancies, placenta previa, as an accompaniment to an amniocentesis, or to confirm gestational age/due dates. Most pregnancies in the US today have one ultrasound at about 16-20 weeks as a matter of course, often to establish or alert the provider as to the normality or potential problems of a pregnancy. In the last trimester, ultrasound may be used to try and determine fetal size (this is controversial as it tends to be highly inaccurate), fetal position for delivery (breech, and sometimes posterior or transverse babies), or in conjunction with other tests to determine lung readiness for early delivery.
Some providers can do basic ultrasounds in their office, but more in-depth ones usually entail a trained ultrasound technician and a more sophisticated machine. The effectiveness of the ultrasound depends greatly on the quality of the equipment used and the skill of the technician using it. Unfortunately, consumer health advocates have found that many technicians (and even doctors) are inadequately trained in using the ultrasound and training is often inconsistent; be aware of this when given any results of these tests. Always get a second opinion (or more) if problems are diagnosed via ultrasound. Also remember that most office ultrasounds are less sensitive than the machines used by ultrasound specialists and perinatologists, so beware jumping to conclusions based on a scan from one of these less-effective machines (for example, a heartbeat very early in pregnancy might well be missed on an office machine, so beware concluding too quickly that there was a miscarriage). If there is any kind of a question about the baby's health or status, get another opinion from a ultrasound expert or perinatologist, and be sure they use a really top-notch machine.
Using ultrasound for dating the pregnancy is generally fairly accurate up to about 20 weeks or so, and many practitioners use it routinely for this purpose in most pregnancies, since many women are unsure when they conceived. This information can be very useful if you are not positive about dates, although it's important to remember that the sizes used to calculate maturity and due dates are based on averages; if your baby tends to run slightly larger than average (as many large women's babies do), then the baby's estimated age may be slightly off. On the other hand, using ultrasound in the last trimester to date the pregnancy, predict a due date, or especially to predict birth size is often highly inaccurate and very questionable, but some providers persist in it anyway. Be VERY cautious about making important medical decisions (like inductions) based solely on dubious data like this. It can occasionally be a helpful tool late in pregnancy--especially pregnancies with lots of complications---but it can also be misused (and has been on many larger women).
A common yet subtle form of size bias is the overuse of ultrasounds near the end of pregnancy in larger women, with the common result of moving up the due date or inducing early because of 'big' baby. All too often these result in a c-section, and usually one that is unnecessary (in some studies inducing women early for 'big babies' resulted in a cesarean rate of 50% or more!). You will want to examine this issue very carefully if a provider proposes using an ultrasound to adjust your due date at all late in pregnancy (or even early in pregnancy if you are sure of your conception dates) or tries to scare you into inducing early because of the baby's size. No study has found a better outcome in women whose babies were induced early for size; most studies actually found a worse outcome instead. Yet this is an extremely common scenario that large women face.
There are two main types of ultrasounds used commonly, vaginal ultrasound and abdominal ultrasound. The first is used for very early pregnancy, and sometimes for heavier women with more abdominal fat. This type is done trans-vaginally, using a long 'wand' (transducer) that is covered with a condom (!), lubricated, and placed inside the vagina. A male technician may ask you to insert it yourself. A female attendant should also be present in these cases. The 'wand' is then moved around your vagina to allow the technician to 'see' up into the uterus and abdomen as needed. Occasionally it needs to be pressed up on either side of your cervix firmly to 'see' the ovaries clearly, which can be a bit uncomfortable for some women, but the discomfort is usually tolerable. Some moms have likened a transvaginal ultrasound to having someone driving a stick shift inside. That’s a crude but accurate description. Having a sense of humor about it makes it easier, but women who have sexual abuse backgrounds may find it harder, and may want to request a female technician instead or avoid having an early ultrasound.
Generally speaking, the trans-vaginal ultrasound is used in the first trimester, since the uterus has not yet grown big enough to lift out of the pelvic cavity. This is common with women of all sizes, not just heavy women, so don't feel like you are being treated any differently at that point. At some point around the end of the first trimester, most average-sized women can have an abdominal ultrasound done, but in some larger women, a transvaginal ultrasound may still need to be used for a few weeks yet. However, every woman is different and many larger women have reported being able to use an abdominal ultrasound at about that time too. Each case will be different and have to be decided at the time, but be aware that transvaginal ultrasounds may have to be used just a bit longer in larger women.
The second type of ultrasound (abdominal) is the type commonly seen on TV shows. It uses a kind of 'mouse' (transducer) attached to a computer and view screen. Your abdomen is coated with warmed lubricant jelly and the transducer is placed on your belly---where on the belly depends on how far along you are. The technician then moves it around as needed to 'visualize' your fetus, its organs, your placenta, your ovaries, possibly your cervix, and also to measure certain key parts of the fetus (abdominal cavity, head circumference, femur, etc.) to determine fetal age. As a woman's pregnancy progresses, the abdominal ultrasound is usually used, commonly sometime after the first trimester. They usually request that you drink a lot of water before one of these ultrasounds in order to help produce a better picture and also to help lift the uterus up out of the pelvic cavity better. However, be sure to ask how much is necessary; sometimes drinking a lot of water is not absolutely necessary and why have that discomfort if it's not needed? Also, drinking lots of water is usually not as necessary later in pregnancy as well.
Many larger women express fears that their providers won't be able to "see through all that fat" during an ultrasound. They feel embarrassed to have someone touching that soft, mushy part of them, the source of so much derision for some people. They are afraid that their fat will somehow make the ultrasound impossible. In reality, however, these fears are largely unfounded. During early pregnancy, nearly all women get transvaginal ultrasounds anyhow, even the skinny women. As pregnancy progresses, average-sized women may be able to use abdominal ultrasounds earlier than larger women, but within a few weeks even the largest woman is able to have an abdominal ultrasound.
Other large women fear the remarks of the technicians or doctors, or fear that the the exam will be less than complete because of their abdominal size. If ANY technician or health-care worker is EVER disrespectful or callous about your size, you should protest immediately, demand better treatment, and report them to their supervisors. ALL WOMEN DESERVE RESPECTFUL, CARING HEALTH CARE, REGARDLESS OF SIZE OR DISABILITY, ETC. No health care worker should ever get away with anything less, especially since they will continue to treat the next large woman badly until someone calls them on it.
Being large can make ultrasounds a bit trickier to do or interpret, it's true. However, this is no reason for disrespectful treatment or callousness. If the technician points out gently that interpreting the ultrasound might be harder, this is a reasonable statement. If they berate you for your size and tell you that there will be no way to know for sure whether your baby is 'deformed' because of all the fat in the way, that is something entirely different! The first is simply important information being passed on to you; the second is a judgment and abusive and should never be tolerated. Some technicians never say a word about abdominal adiposity (fat) but others may list the exam as being somewhat incomplete since it's possible for adiposity to interfere with images. Usually, however, it is not a significant problem, and this reason may be listed just for liability purposes. If in doubt, ask. It is not usually a big deal for most large women.
Sometimes, though, doctors and technicians can be rougher in an exam with a larger woman because they feel that they must press down extremely hard in order to compensate for adiposity, which can be really uncomfortable. However, personal technique has a lot to do with comfort level. Many larger women who have had multiple ultrasounds report that it hurts more with some technicians than with others. Why should it hurt with some providers and not with others? Perhaps these providers are assuming unnecessarily that extremely firm pressure will be needed. The best approach is to acknowledge tactfully that adiposity can cause problems, but that you'd prefer it if they started more gently at first, and then increase pressure only if and when needed. Most technicians, if approached nicely, will agree to this.
It's also important to note that pushing too hard can sometimes cause distortions in what the technicians 'see'. Some large women have had the experience of the technician pushing extremely hard, then being told that their baby had problems. If you are told that your baby has deformities or other problems based on an ultrasound scan and they seemed to be pushing hard, ask for the scan to be repeated with a transvaginal scan or by a perinatologist (who tends to have the most advanced equipment).
Jessica's Story (paraphrased): I had an ultrasound at 18 weeks. I was told my weight made it impossible to scan the baby, and they saw encephaly on the scan. They told me he was going to have a grossly misshapen head and that I'd need a c-section. They sent me to a high-risk OB. He saw the scan and said, "Wait a minute, you're pushing too hard! Do a vaginal!" They did the vaginal and there was our rascal, safe and sound, the right size, and no deformity. I was sore for a week after the abdominal scan, the transducer hurt so bad.
Ask for a transvaginal if they start to push too hard, or ask your OB to send you to a perinatologist for a better scan. What happens when they push too hard is they distort and add artifact to what they can't see, and the baby looks deformed to their measurements.
There are also a couple of further refinements that can be done if the technician has difficulty resolving the images adequately. First, if you have a large 'apron' (belly that sags somewhat), they may ask you to pull it up a bit and hold it back, especially if you are around the end of the first trimester/beginning of the second trimester. This is when getting abdominal images is tougher anyhow and the uterus is lower down, so pulling up the belly a little (if necessary) might make sense in this instance. Don't be embarrassed. Your body is simply your body, and it's not that uncommon in diagnostic tests to have to pull and push things this way and that a bit. Be matter-of-fact about it and just do it. If this is unable to resolve the image, they may need to go to a trans-vaginal ultrasound instead, but remember that this is very common around this time period and nothing to be embarrassed about. It's simply a matter of finding the right technique for the job.
Another technique they can use to clarify images later in pregnancy is to put the transducer (or use the vaginal transducer wand) inside your belly button. This is reportedly uncommon and a little uncomfortable, but if there is an image that needs clarification that they are having trouble finding, some research has reported success with this. Few mothers would object to it if it meant being able to resolve a question of their baby's health! It is usually not traumatic, but like the other types of ultrasound, can involve a bit of pressure and pushing. As with the abdominal ultrasound, ask the technician to start more gently and then increase the pressure only if needed.
Ultrasounds can be a very useful tool in certain situations. However, they are overused in US society, raising the costs of healthcare significantly and unnecessarily. In addition, there have sometimes been questions about their safety, so while it can be emotionally very rewarding and reassuring to have many ultrasounds in a pregnancy, it is probably best to avoid having many unless medical circumstances dictate it. It is Kmom's personal non-expert opinion that one ultrasound is probably reasonably safe to have in a pregnancy, but that unless there are extenuating circumstances, it is probably better to err on the side of caution and limit ultrasounds only to one or those truly necessary. The risk is probably not very large, but if it is not truly necessary, it's better to be cautious. And many women do choose to never have a single ultrasound during pregnancy---it's not a requirement by any means. If you do have an ultrasound there is no need to feel guilty, but neither should you be pressured automatically into one either. Like any other test, it's simply a matter of choice.
Although many larger women are anxious about their ultrasounds beforehand, most find the experience to be no big deal. You might want to inform the technician when making the appointment that you are a larger woman and would like someone more experienced with using ultrasounds on larger women. If you are uncomfortable with the thought of a male technician, feel free to request a female one; this is not unusual and should not be a problem. Remember to acknowledge that ultrasounds can sometimes be a bit harder with larger women but request that they start with more gentle pressure at first and only increase the pressure as needed. If you are upfront and matter-of-fact about your concerns, most technicians will respond positively and work with you to make the experience more pleasant.
If you want to find out more about ultrasounds, be sure to visit the FAQs at misc.kids.info. There are also other sites that deal with ultrasound information, including http://home.hkstar.com/~joewoo/joewooz.html, which gives general ultrasound information and what it measures. Another is www.ucsf.edu/daybreak/1998/03/326_ult.htm, which gives information about how ultrasounds can be used to help detect Down Syndrome in some cases (what appears to be a space in that URL is actually an underline). There are many other sites out there as well, though site addresses change all the time, so you might want to do a search online to get more (or more updated) information. Either way, however, ultrasounds generally do not need to be a stressful or unpleasant experience for women of size, but as with any woman, they should not be done for trivial reasons.
AFP tests (alpha-fetoprotein tests) and the newer triple screen (or multiple marker) tests are used to screen for possible birth defects in fetuses. This test is usually taken around week 16 (anywhere from the 15th -18th week of gestation) after your Last Menstrual Period (LMP). Alpha-fetoproteins are produced by the fetus. The amount is measured in the blood of the mother through a simple blood draw from her arm; a too high reading MAY indicate a Neural Tube Defect (NTD) such as spina bifida or anencephaly, and a too low reading MAY indicate Down's syndrome. However, an abnormal reading on this test does NOT tell you that your baby has a birth defect for sure; it only indicates the need for further testing. This test is simply a screen to find when further testing is indicated; it does NOT tell you whether or not your child has that birth defect at all.
It's vitally important that women understand the difference between a screening test and a diagnostic test. Because tests that diagnose conditions like birth defects or gestational diabetes etc. are very time-consuming and expensive to do, using them for every pregnant woman is simply prohibitive. It is not practical. Some providers prefer to do little or no testing (since every test has its strengths and weaknesses), but since most OBs are very technology-oriented, they often prefer to offer a screening test instead. This test looks for results that indicates women statistically more likely to have the problem, so that a selected group can be tested more carefully and thoroughly but so that ALL women do not have to have the diagnostic tests.
However, by nature a screening test will miss a few cases of the problem, and also identify a number of women as needing further testing who will actually turn out not to have the problem. The strength of the screening test is that it identifies some cases of a problem that might go undiscovered with no testing, and is much less time-consuming and costly than universal testing because it narrows the field of who should be further tested. The weakness of a screening test is that a few cases will be missed, and many women will be subjected to the worry, trouble, and expense of a diagnostic test when there was no problem in the first place. These are the tradeoffs inherent in prenatal testing; some providers feel that the benefits are not worth the weaknesses of these tests and use them only very selectively or not at all. Even many OBs now are questioning the worth of screening all pregnant women, but at this time, screening tests remain more common than not. Therefore, it's vital that we understand them better.
A bit more terminology needs clarification here. Many people use the term 'false-positive' for the case where a woman's screening test was 'positive' (i.e. there might be a potential problem and further diagnostic testing is needed) but the testing result on the diagnostic was 'negative' (i.e. the diagnostic showed that there was no problem and everything was normal). By definition, the term 'false-positive' is a misnomer, since the screen wasn't false, it only pointed out a need for further testing. It didn't say there WAS a problem for sure, only that more testing was needed.
So the phrase 'false-positive' is not a very accurate term to use, but the problem is that there is no proper substitute that is short, concise, and easily used. Since medical research does continue to use the term 'false-positive' despite its obvious problems, the same phrase will be used here as well, although with strong reservations. It's also worthwhile to point out that sometimes high screening results (even with a normal diagnostic result) can be a marker for other possible problems in a few cases. Be sure to discuss these concerns with your provider.
According to some sources, about 5-10% of women will have a positive initial AFP test, while less than 1% of the overall population will have a baby with birth defects, so there is quite a high rate of 'false positives' in the initial screening. (Different sources list different percentages of women who need further testing.) These women with 'false-positives' will be put through weeks of worry about whether their baby has a congenital birth defect; many will go through an amniocentesis as a result, which also carries a small but definite risk of miscarriage as well. They also face the daunting prospect of whether to terminate a pregnancy that is already far along if the baby does turn out to have problems. Since a 'false-positive' on the screen means weeks of emotional angst, yet very few of these will turn out to actually have a problem, many women elect not to do this test at all.
In spite of the high rate of false positives, this test does detect enough birth defects that most physicians now routinely offer it. It is not required and many women choose not to opt for it due to this false positive rate, or because of reservations about terminating a pregnancy with birth defects. The addition of the triple screen test in the last few years has helped eliminate some 'abnormal' screening results, so you might want to consider this version instead if you really desire this test. Various kinds of triple screens are available; some involve measuring hCG (human chorionic gonadotropin) and estriol levels as well as alpha-fetoprotein levels. It is not clear yet which combination of tests is most accurate, but they are thought to be more accurate in predicting Down's Syndrome (not neural tube defects). More information on the various test types can be found on the misc.kids FAQs and from your health provider. The actual types of tests vary from year to year as researchers search for the 'magic bullet' that will give the most accurate answers with the fewest 'false positives', so be sure to do up-to-date research every time, and be sure to discuss its value carefully with your provider. Ask LOTS of questions and be sure to consider all the implications thoroughly.
The usual recommended follow-up for an 'abnormal' screening result is a higher-level ultrasound, to see if abnormalities can be detected. Genetic counseling is also usually offered to help determine risk. Using complicated mathematical formulas, risk level is determined from the data available, and further testing in the form of amniocentesis may be offered. Results usually come back in about 2 weeks. Be sure to research carefully the risks involved in amniocentesis before making any decision. See the section on amniocentesis for special concerns big moms may have with amnios.
Maternal weight and fetal age are critical issues in getting accurate results. Weight is part of the mathematical formula used to figure the risks involved, so it is critical that it is accurate. Because larger women have greater blood volume due to their size, the amount of AFP from the baby becomes more 'diluted' in their blood, tending to give an artificially low result. Extremely petite women have the opposite problem---because their blood volume is smaller, the AFP from the baby is more concentrated and they have more artificially high results. A number of studies have documented that large women tend to have more 'low' AFP results (risk of Downs) and very small women tend to have more 'high' AFP results (risk of Neural Tube Defects) [See references.]
Because of this, most labs now apply 'correction' formulas to lab results for very large and very small women. The purpose of this is to decrease the high number of so-called 'false-positive' results in these populations. However, not all labs use the same correction formulas, which means that some labs will have higher rates of 'false-positives' than others. In addition, some labs have even been documented to over-correct for size, so that some large women have been given false-positives for 'high' AFP levels (risk of Neural Tube Defects) because the lab over-corrected for their size.
Therefore, large women should be very cautious about whether to take these tests, and also be cautious about how seriously they take a 'positive' screen if they do decide to take the AFP test. Large women have had a higher rate of 'false-positives' in the past, causing many women extreme distress unnecessarily. On the other hand, some women feel it is very important to know ahead of time if there is a problem, and some women would choose to terminate a pregnancy in that situation. In other cases, knowing a diagnosis ahead of time can help determine treatment and birth protocols, even if you would not consider ending the pregnancy. For these women, taking the AFP test may still make sense.
Remember that whether you take this test is a matter of complete personal choice. It is an optional test; feel free to decline it if you wish, or to take it if you wish. If you choose to use the AFP test, your weight should be measured ON THE DAY YOU TAKE THE TEST, right beforehand. Try to use the scale that is consistently used for your weigh-ins at your health provider's office. An accurate weight will be critical in determining the amount of 'correction' the lab will apply to your results, so be sure to insist on a very accurate weight, taken on the day of the test. You should also strongly consider taking the 'triple test', which contains multiple markers that are measured. Since large women are more likely to get a result that is low and indicates a possible chance of Downs Syndrome, a triple test is usually a good idea, since it measures more than one parameter and tends to eliminate at least some cases of 'false-positives' for Downs. In addition, there may be new tests that can be added to help increase accuracy (i.e. the new 'nuchal transparency' test with ultrasound, see below).
Dating the pregnancy accurately is also EXTREMELY important in eliminating false abnormal results. Most labs date via a woman's Last Menstrual Period (LMP). This assumes your cycle to be about 28 days long, and assumes you ovulated on about Day 14. If your cycle is significantly longer, you probably ovulate later than Day 14, and your baby may be younger than the LMP figures would indicate. This can skew results significantly---even a few days can make a difference. However, many labs refuse to take into account differing cycle lengths and will only go by the LMP, since many women are not sure exactly when they usually ovulate or when they conceived that cycle. This can cause problems in interpreting the results correctly. Be SURE your health provider is aware of this potential problem if your cycles run shorter or longer than 28 days or are irregular. If you are not yet pregnant, you should strongly consider charting your temperatures and cervical mucus so that you will know for sure when you conceived. Being able to date the pregnancy accurately can save a lot of problems during prenatal testing and around delivery time!
Many larger women are being pressured strongly into taking the AFP test since the 1996 research on neural tube defects in the pregnancies of large women came out. A whole section of this web site is devoted to discussing this research in more detail (see Neural Tube Defects: Don't Panic!). However, a quick summary is that several retrospective studies showed that larger women's pregnancies may be more at risk for neural tube defects. However, these results were preliminary, don't address cause, and critics have voiced a number of reservations about them. Furthermore, a much larger and more definitive follow-up study did NOT find an increased risk for NTDs in larger women, so this is by no means an established relationship. But even if the studies did turn out to be true, the risk of large women having a baby with a neural tube defect is less than 1%. So large women should not feel pressured into having an AFP test just because of the results of this research, especially considering the higher rate of 'false-positives' for larger women in some labs. It is simply another option to consider, not a requirement because of size.
Some women choose a compromise position; they are uncomfortable with the high rate of 'false-positives' on the AFP/triple test, but do not want to go completely unscreened in pregnancy either. Many of these women choose instead to have more detailed ultrasound, called a Level II Ultrasound, in which the technician will look carefully for problems in the spinal cord, heart, etc. which might indicate a neural tube defect or Downs. The advantage of this is that it's less involved and finds many cases of problems without the worry and trouble of the AFP test, and if a woman has a positive AFP screen, one of these tests will be ordered anyhow. However, not all problems can be found with even a Level II ultrasound, and sometimes adiposity can interfere somewhat with ultrasounds. If this is a choice you are considering, be sure to discuss with your provider the strengths and weaknesses of choosing only a Level II ultrasound.
A relatively new test that is just beginning to be used regularly is the Nuchal Translucency Scan. In this test, an ultrasound scan at about 12 weeks is performed, and the thickness of tissue fluid under the skin at the back of the baby's neck is measured. Using this measurement, the length of the baby, and the mother's age, the risk for Down's Syndrome for that baby is computed. If the risk is more than 1 in 300, then an amnio can be offered. In preliminary studies, this test had a detection rate of 80% from the scan alone; 90% if other blood markers (Pregnancy-Associated Plasma Protein A or PAPP-A, plus free beta subunit of human chorionic gonadotropin or B-hCG) are also checked. Another advantage of this test is that it is done earlier, and in the best-case scenario, results can be available to the parents before the end of the first trimester.
Although many women feel comfortable with the compromise of only a Level II ultrasound, it will not catch every problem and is not a guarantee of a 'normal' child; many women do go ahead and choose the full battery of AFP tests, level II ultrasounds, and if necessary, an amniocentesis. Of course, none of these choices is 100% accurate either, and there are never any total guarantees. No choice is absolutely right or wrong; you have to decide what is most appropriate for YOU in your situation. It is a very personal decision, and you may want to consider what actions you would take if a problem were found. This may help you decide whether to take the test at all. Remember that if you receive a high or low result in the initial AFP screening, all it means is that a closer look is needed. The odds of still having a ‘normal’ baby are strongly in your favor, even with a 'false positive' on the first test.
AFP testing can be tremendously stressful, even though the chances are very strongly in your favor that your baby will be normal anyway, but for some women the security of knowing with at least some more certainty is more important than the stress of taking the screen. It’s vitally important to be well-informed about this decision either way. For some women, choosing NO testing at all is the right choice, others will choose the full battery of tests, while still others will find some compromise between these two. Different choices are appropriate for different women, but it's important to remember that all tests are OPTIONAL and not required, that each testing choice has its advantages and disadvantages, and that you should never allow yourself to be pressured into (or out of) prenatal tests you feel strongly about.
Kmom's Story: As a matter of course, I was offered the 'opportunity' to take an AFP test in my first pregnancy. I was uncertain about what I should do, but although no one forced me to take the test, I was certainly strongly encouraged to do so. I agreed without really understanding the full implications of the test and the possible decisions it could force. I figured the doctors knew best. Then the test came back as having abnormally low AFP---at risk for Down's Syndrome. Nobody in the doctor's office bothered to tell us that this was quite common and that statistically the baby was probably normal. They provided virtually no counseling or reassurance at all, worrying us in the extreme. Nor did they consider my longer cycles, even though they clearly knew about them, or tell us that larger women have a higher rate of 'low' false-positives. Since we knew none of this information, we went ahead with an amniocentesis, basing our decision mostly on anxiety instead of on facts since they gave us no extra information or emotional support. Had I been counseled on the high probability of a 'false positive' or on the possibility of longer cycles or size increasing false results, I might not have taken the test, or at least been more prepared for an adverse result.
In addition, I am adopted, and not knowing if there was a history of Down's Syndrome in my biological family made the process even more fraught with anxiety. Since I had little medical history information, I was basically treated as if I must have had a positive family history for it. The genetic counselor was nice enough, and did spot the possible influence of my longer menstrual cycles, but by then we were so terrorized we went ahead with the amnio despite the possibility it wasn't necessary after all.
The actual amnio was quite unpleasant (see below) and caused bleeding and cramping, giving rise to more anxiety that I might miscarry a healthy baby. Plus there was the awful anxiety of the terrible decision of what to do if the amnio results were abnormal. I could not bear to think of ending the pregnancy when I could feel the baby moving and had bonded with her already, but there was a great deal of pressure on me from others to reconsider the pregnancy. The weeks of waiting (over Christmas, yet!) were the worst of my life. It was AWFUL. Having these tests robbed me of much of the joy of that period of pregnancy for me, and it really does alter the way you experience pregnancy. I would never want to repeat this experience.
Fortunately, the amnio results showed that the baby was normal, but it took a long time to recover from that scare. I later found out that the lateness of our testing meant that if we had wanted to terminate the pregnancy (we didn't, but most women do terminate pregnancies with birth defects), it would have been almost too late, and the procedure to terminate would have been much more complex and difficult. Yet no one informed us of this at any point. I certainly don't feel that I was truly aware of what the test meant and its possible implications when I was pressured into taking it. It took a long time to emotionally recover. And although in hindsight the test meant very little in terms of the health of my pregnancy, emotionally it changed my perceptions. It made me perceive my pregnancy as more high-risk, made me mistrust my body's ability to gestate and birth normally, and made me doubt myself and my judgment. It reinforced an over-reliance on technology for answers, and disempowered my image of myself as a healthy birthing woman. Others may not experience it that way, and certainly I didn't feel that way ahead of time when I initially took the test, but that was the net effect that it had on me. It really took a lot of the joy from me about my pregnancy during what should have been one of the most wonderful times of my life.
With my second pregnancy, we charted my cycles so as to know exactly when we ovulated and conceived, which was over a week later than the 'usual' interval of 14 days. Although I was hesitant to take the AFP test again, the staff convinced me that figuring in my longer cycles and adding 2 additional tests (the 'triple screen') would improve its accuracy. Since I was 35 at the time, I agreed to the test. When we took it, we clearly marked that I ovulated on day 22 or 23 instead of on day 14 and therefore they should date the pregnancy differently, but the lab crossed out our refigured dates and based their results on my LMP instead. Even with charted proof their policy was that you could not 'trust' a woman to know her own cycles.
As a result, although I was in my 17th week, the lab figured I was well into my 18th week. This made them expect a higher level of AFP in my blood, and when it was lower than they expected, my results were labeled as being at risk for Down's again. The nurse checked, and the lab confirmed that they refused to consider my longer cycles when figuring my results. When the nurse protested, the technicians told her to resubmit the paperwork, and this time to LIE about my LMP, delaying it by one week in order to make the fetal age correct. This time the results came back as being of appropriate levels for a fetus in week 17. (In addition, the ultrasound we did around this time for other purposes confirmed that all appeared normal.) Thus we didn't face the choice of whether to do another amnio, which we would have faced had we not known to adjust the lab's information. We almost certainly would have refused another amnio given the negative experience we'd had the first time around, but did not have to make that choice this time. Thank goodness the nurse knew to check the dates and was willing to resubmit my paperwork, but how ridiculous to have to LIE about my LMP in order to get accuracy!
In my third pregnancy, I was 38 and knew I would face a lot of pressure to do these tests due to my age. However, the ordeals I had been through in my first and second pregnancy reinforced the research that I did later on, and I chose NOT to do a triple screen/AFP or amnio in this pregnancy despite my age. The fact that I knew for sure that I would not terminate the pregnancy even if a problem was found just reaffirmed that decision. However, I did choose to have an ultrasound so that if an obvious problem were found (i.e. obvious spina bifida, etc.) I could have time to research the best decisions about pregnancy treatment and birth, etc. I also felt that given my past two cesareans and the fact that this can cause placenta problems in future pregnancies, it was important to establish placental normality. So I did choose an ultrasound, though I did wait until near the end of the second trimester to minimize exposure to the developing baby and to minimize the possibility of misdiagnosis of a low-lying placenta (most of those diagnosed early move up as pregnancy progresses and are rarely a problem).
I chose to see a midwife that was not big on lots of prenatal testing so that I would not face a great deal of hassle about my choices. I must say that this decision made this pregnancy much more enjoyable and peaceful. I felt like I could really enjoy the pregnancy and concentrate on bonding with the baby, and I would choose the same for another pregnancy, even though I would be 40 or more at the time. I felt like choosing an ultrasound but not other testing was a good compromise for the beliefs and priorities that were important to me.
This is not to say that the AFP/triple screen (or the next tests they are developing) are never appropriate, or that women who choose to have them are wrong for doing so. Some women make very informed choices to take these tests and I respect that decision. Under certain circumstances, I might also choose to take these tests. However, I also see many women pressured into taking these tests without really understanding their implications, and I see many pregnancies traumatized unnecessarily by the all-too-common experience of a 'false-positive' result. I urge women to carefully consider the full implications of all of these tests before deciding whether or not to take them.
The point is that the AFP can be affected by a number of factors, including maternal size, fetal age, and maternal cycle length. These can make a HUGE difference! An excellent, non-judgmental resource for considering all sides of this decision is The Tentative Pregnancy, by Barabara Katz Rothman, available from www.1cascade.com or www.birthworks.org. If you do experience an alarming test result, another good resource is Precious Lives, Painful Choices: A Prenatal Decision-Making Guide by Sherokee Ilse, available from www.1cascade.com. And be sure to discuss these issues very carefully with your health provider! -------KMom
Amniocentesis is the process of inserting a needle into the uterus to withdraw some amniotic fluid from around baby for testing. A baby's chromosomes can be examined this way for defects. It is commonly used for checking for problems such as Down's Syndrome. The needle is inserted through the mom's abdomen and into her uterus, and ultrasound is used to be sure that the needle does not come in contact with baby. Results usually take about 2 weeks to arrive although sometimes you can get some preliminary results sooner. Complications can include cramping, bleeding, and sometimes even miscarriage, so risks must be weighed carefully. It is wise to be very cautious in deciding to use this test.
Checking for birth defects is not the only reason amnios are done, but it is the most common one. Sometimes an amnio is done at the end of pregnancy to see if the baby's lungs have enough surfactant, which is needed for baby to start breathing on its own after delivery. If your health provider is considering an early delivery for you because of pre-eclampsia, gestational diabetes, or other problems, an amnio may be recommended to determine lung readiness. However, be sure to question closely the necessity of an early delivery by induction or C-section. Early delivery can be lifesaving and very appropriate in many cases, but management protocol of many pregnancy problems change over time, and recommendations may vary between doctors. Some elective early deliveries may be questionable. If in doubt, seek a second opinion and do the research. If you feel confident that it is necessary, proceed, and don't hesitate to do a late amnio to check the baby's lung maturity if needed.
Due to the risks, amnios are not recommended for the general population until the mom is at least age 35, unless there are special circumstances. Do not assume, however, that you MUST have an amnio if you are over 35 or for any other reason. Any and all tests are always OPTIONAL; you do have the right to refuse them if you wish. While the risk of problems does increase with age, these risks can be overemphasized; the odds of having a healthy baby are still greatly in your favor. Amnios are an effective tool under certain conditions but should not be used routinely. Personal beliefs may play a large role in your decision as well. Be sure to discuss thoroughly all aspects of the decision and the procedure with your health care provider; it is not a decision to make lightly.
The implications for larger women in an amnio are unclear. Physically, it is possible that the test may be harder for the doctor to do because of abdominal adiposity (fat). However, many large women (including 'supersized' women) have had the procedure done without problems, so it is definitely possible. Ask your doctor for more information before you begin, and find out what kind of experience he/she has in performing amnios on larger women. For women with very significant abdominal adiposity, it has been suggested that a longer needle may be desirable---see the section on Facilities and Equipment. In addition, some very large women have found that waiting a bit longer (after week 18-20 or so) makes the procedure more effective on large women, although if you would consider terminating a pregnancy based on the amnio results you might not want to wait. You may want to ask your health provider to look into it.
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 the low AFP test result. 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. The atmosphere in the room was 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, and was scared to death that the baby would be 'normal' but I would miscarry anyway. Fortunately, everything turned out fine, but it was a scary couple of days.
Afterwards, he mentioned briefly the uterus contraction but mostly blamed my abdominal fat for his difficulties, which though ample in me was not really huge. Still, I felt terribly guilty. 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. I also 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 was not very kind about it either. Yet many women much fatter than I have had amnios without any problems at all, so 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 primarily 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 due to 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 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 and unkind 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. 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 feasible. 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. 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 a bit more challenging to perform, but it is the duty of the doctor to be prepared to treat ALL women, regardless of circumstance. ---------------------Kmom
This section is a very short summary of the tests for gestational diabetes, since this is part of the usual battery of prenatal tests given to most pregnant women (and especially heavy ones). However, gd and its testing is a very complex subject and cannot be covered thoroughly enough here. Readers are strongly urged to consult the websection on this site devoted to Gestational Diabetes; there is an entire FAQ devoted simply to issues about GD Testing. Other websites also have quite a bit of information about gd and its testing; a list of some of these websites can be found in the "Introduction to GD" and "What Is GD?" FAQs.
Basically, gestational diabetes (as currently defined by the traditional medical establishment) is thought to occur when placental hormones overwhelm the capacity of the mother's pancreas to produce enough insulin to keep her blood sugar in the 'normal' range. All pregnant women experience some degree of carbohydrate intolerance due to hormonal influences, but most women are able to compensate enough to keep their blood sugar in the normal range. A few women (about 4% of the overall U.S. population, more in some areas and groups) have too much resistance to their own insulin and/or produce too little insulin to compensate for these hormones, so blood sugar rises above what some doctors have decreed as 'normal'.
It is clear that at very high levels, high blood sugars can be quite harmful to the baby. However, there is a great deal of debate about whether mild degrees of this is truly a concern, or at what point concern is justified. Some researchers contend that mild carbohydrate intolerance in pregnancy is the pregnant system's way of adapting to the higher energy needs, and in mild degrees it does not warrant any additional concern. Critics often also contend that treatment for 'gd' tends either to not improve outcomes or actually worsen them in some cases (i.e., a very high rate of c-sections). It is true that research on gd tends to be mixed, and that not all countries around the world believe in doing routine 'gd' testing. However, most providers here in the USA have bought into 'gestational diabetes' as a disease and so test for it routinely in pregnancy.
A debate over the relative risks and benefits of the gestational diabetes diagnosis and of routine gd testing can be found on this website under the section, "All About Gestational Diabetes". In contrast, this summary is simply an explanation of very basic information about gd testing. However, as with other forms of prenatal testing, it's important to note that not everyone agrees with the value of such testing, and some people decline it. It is certainly within your right to decline testing, but it does make sense to be very cautious in eating and exercise habits if you decline the testing.
About the 28th week of pregnancy, most providers (but not all) have the mother take the one-hour screening test for gestational diabetes. The test is given at about this time because most of the critical hormones that tend to raise blood sugar peak just before this time. The test may be given earlier if the mother is deemed to be in a 'higher-risk' group, such as ethnic groups like Hispanics or Native Americans. Large women are also deemed to be at higher risk for gd, so they are often tested in the first trimester or early in the second trimester in addition to the later test. The test may also be repeated in the third trimester for those deemed to be at extremely high risk for gd, since one other hormone (progesterone) peaks at about that time and may tip a borderline woman over into 'gd'.
The first test is simply a screen (see the above discussion about screens vs. diagnostic tests), designed only to find a group of women that need further testing. It does NOT mean that you have gd, only that you need another test! About 85% of the women who 'fail' the one-hour screening challenge test will actually 'pass' the three-hour diagnostic Glucose Tolerance Test, so don't panic if you 'fail' the first test. Chances are you will still 'pass' the second. Only 15% or so of the women who 'failed' the initial screening test will also 'fail' the diagnostic test and be labeled as having 'gestational diabetes'. However, even if you 'pass' the second test, it would be appropriate to be more cautious in your food intake (much less sugar and refined carbs, limiting overall carbs at any one meal, more protein more often through the day, eating a small snack every 2-3 hours, more exercise, etc.).
The most common screening test is the 50g Glucose Challenge Test. In this test, you are given a kind of 'soda-pop' (usually orange- or cola-flavored) which contains 50g of glucose (sweet sugar-water, more or less). After exactly one hour, blood will be drawn from your vein and the plasma tested to see how high your blood sugar is (a few offices use a hand glucose monitor instead, adjusted to read plasma-like results). If your results are >140 mg/dl, you are deemed to be in need of further testing. Because the cutoff of 140 mg/dl means that about 10% of gd cases will be missed, some providers routinely use a lower cutoff in groups at higher risk, such as older women, heavy women, women with a history of diabetes in the family, or women from certain ethnic groups. In these cases, a cutoff of 130-135 mg/dl may be used; in rare cases a few providers will use cutoffs in the 120s, though this is certainly extremely conservative.
Officially, the 50g challenge test is given without regard to the time of day, to when you have eaten, or any other circumstance. However, research shows that results can be thrown off by a number of factors, including illness, great stress, smoking, certain medications, being bedridden, etc. It's probably best to take the test in the middle of the day, having had a good breakfast or lunch with plenty of protein, but having let at least 2-3 hours pass since you last ate. Officially it's not supposed to make any difference whether you just ate or not, but it only makes sense that if you are trying to process the 45g of lunch carbohydrates you just ate along with the 50g of the glucola drink, you might tend to have a higher test result. So, while you should never try to fool the test, it doesn't make sense to go in and take the test in a way that might raise your results falsely.
Before the test (and indeed all through your pregnancy) you should have been exercising on a regular basis and eating healthily. You should not take the test when you are ill, when you are greatly stressed, had a really bad night, etc. Again, technically, the rules say that the 50g challenge test should be given without regard to any of these circumstances, but Kmom disagrees and feels that the test should NOT be given right after a meal or when the mother is abnormally stressed or ill, since these will raise her results above normal levels and possibly force additional testing that might not have been needed. However, neither should you try to 'fool' the test by suddenly running out and changing a bunch of habits. Your results should reflect your normal lifestyle and what presumably would be your normal blood glucose (bG) readings after food. This is very important--don't try to 'fool' the test.
If your one-hour screening challenge results are above the cutoffs listed above, you will then be given the actual DIAGNOSTIC test, the three-hour 100g Glucose Tolerance Test (GTT). In this test, some authorities tell you to prepare by emphasizing carbohydrates in your diet for 3 days beforehand (carbo-loading) and being active and exercising normally. Then you fast overnight for 8-12 hours before the test. Only water is allowed during this fast, and the timing is very important too. Then at the lab, a fasting blood draw is taken, and you are given more of the glucola to drink, only this time it is twice as sweet with a 100g sugar load. Then your blood is drawn at timed intervals, most commonly after 1 hour, 2 hours, and 3 hours, although a few labs have some variations on this. The plasma is separated from the blood, and sent to the lab for testing.
The GTT is the only test that can diagnose the condition of gestational diabetes as currently defined; if your doctor tries to treat you as having gd on the basis of your one-hour challenge test alone, you are being misdiagnosed. ONLY the GTT can be used to diagnose gd. There have been cases in the past, particularly for large women, where the doctor gives the one-hour challenge test, the result is borderline or close, and the doctor diagnoses gd from that borderline or slightly high result and goes straight into treatment, skipping the 3-hour test. THIS IS INCORRECT TREATMENT. Except in very rare cases, the full three-hour GTT test must be given in order to diagnose gd. Remember, only 15% of the women who 'fail' the screen actually 'fail' the full GTT and end up being diagnosed with gd! So if any doctor tries to bulldoze you into a gd diagnosis without doing the full GTT, you need to find a new doctor, pronto! And especially so if he tries to justify it because you are in a 'higher-risk' category. The standards for diagnosis are the same, no matter the person's ethnicity, size, family history, etc.
Of course, there are occasionally exceptions to every rule, and there are two exceptions to the rule that all women with a positive screen must have a 3-hour diagnostic too. The first exception is when there is a very high result on the challenge test. The cutoff is 140 mg/dl; if your results on the 50g challenge were well over 200 mg/dl, it's safe to say that you have gd and should proceed directly to treatment. Some doctors have proposed a cutoff of 185 mg/dl for 'diagnosing' gd on the screening test; Kmom is not in agreement with this and feels women between 185 mg/dl-220 mg/dl should proceed with the GTT. However, that's simply her opinion and not medical advice; some doctors would disagree with her. You can read more about this controversy in the websection on this site on GD Testing.
The second exception involves testing protocols outside the USA, which are not the same as in the USA. Most providers outside the US use one 75g two-hour test instead of the double test (50g screen and 100g GTT) used in the US. The advantage of this is that only one test is needed instead of two, although medical professionals have been arguing over the various testing protocols for years now. The reality at this time is that providers in the US generally use a 2-tiered testing system of a screen and diagnostic GTT, whereas those outside of the US generally use simply one 2-hour diagnostic GTT. The cutoffs for diagnosing gd on the 75g GTT vary from provider to provider. The 4th International Workshop-Conference on GD has called for cutoffs of about 155 (8.6 mM) after 2 hours on this test, but this is a very conservative body and many providers differ, so you will have to consult your provider for his/her specific standards. Requirements for the 75g are extremely nonstandardized around the world and will vary widely.
It's important to note that these exceptions are not likely to be encountered by most US women being tested for gd. Most US women will have the one-hour 50g challenge test, and if their results are around 140 mg/dl or more, they will have a follow-up diagnostic GTT with a load of 100g. Gestational Diabetes is diagnosed when two or more of the cutoffs are exceeded, unless the fasting is extremely high in which case only that reading is needed to diagnose gd. A few providers will diagnose gd on the basis of just one elevated level, but this is not the official policy. The scale used for determining the cutoffs varies from provider to provider; the American College of Obstetricians and Gynecologists uses a scale of 105 fasting, 190 at one hour, 165 at two hours, and 145 at three hours. Other providers recommend stricter cutoffs for various reasons; you have to ask your providers exactly which scale they use and why. See the GD Testing section for further discussion of these various cutoffs and their pros and cons.
If you have been diagnosed with gestational diabetes, you should realize that it's not the end of the world. Chances are everything will be fine and you just need to be more careful about your food intake and exercise more. However, it's also important to realize that providers vary TREMENDOUSLY in their treatment protocols for gd, and the recommendations you will be given for your care from your provider might well be completely different from the recommendations you would get from a different provider. With gd at this time, little is written in stone. If you are diagnosed with gd, it would behoove you to do a great deal of research into the issues around gd so that you can participate in your own care decisions. Resources for doing more research can be found in the GD section on this website, where there are also links to a number of other sites and to Medline for you to do your own research.
Kmom's Story: I was diagnosed with gd in my first pregnancy (not my second or third pregnancies, however). Because of my size and the lack of family history from being adopted, they assumed I was very high risk for gd and tested me early in pregnancy, but with very little information about the test and how to take it. The screen came back slightly below the cutoff so to be cautious they ordered the full 3-hour test. They didn't bother to tell me it was a fasting test this time so I had to reschedule and come back yet another time. The test itself made me ill and was certainly no fun, but at least I 'passed' it. At that point, they should have offered me some nutritional advice to help me lessen my risk of getting gd later on, but nothing was said, and I was told that it didn't matter if I didn't eat when I felt nauseous. This made my blood sugars start to swing greatly, increasing my nausea and probably predisposing me to greater blood sugar abnormality. I believe strongly that with a little more nutritional guidance I might have avoided getting gd later on. This lack of emphasis on prevention is a very sore point for me, considering everything that the 'gd' label led to for me.
In the second trimester, I retook the screening test. Once again I had no instructions on it, and took it during a time of great stress (I was packing up my house and job to move). Again the results were borderline (just slightly above the cutoff this time), so again I took the 3 hour GTT. This time I knew to fast, but I didn't know that illness could affect the test. So I took the 3 hour test while I was sick, stressed, and after having been at 2 baby showers that week, complete with cake and punch---more sugar than I normally consume. I failed the 3 hour test this time, but it's hard to say whether those results were really reflective of my true condition or not. The stress, extra sugar, and especially the illness may well have made my results higher than normal.
I was diagnosed with gd, put on a special food plan, and nearly put on insulin as I tried to cope with all of this while moving to a new state. Fortunately my blood sugar settled to normal once I got established in my new place and my stress dropped off. However, my pregnancy was now labeled as 'high-risk' and most OBs I interviewed wanted to induce early. I chose the only OB who would 'let' me go to term, and he induced right at 40 weeks, even though my cervix was not ripe. It was a long and very hard labor, with lots of hassles because of the gd. I ended up with a c-section, and a very traumatic one at that. My baby was automatically given formula at birth (against my wishes!) because of my gd----even though her blood sugar was normal----and breastfeeding got off to a rough start. They also were extra cautious and put her in the intensive care unit one night to be sure her heart was okay, since sometimes gd babies can have potential heart problems. The mere label of 'gd' made them induce which led to a long rough labor and then a cesarean, put all kinds of restrictions on me, made them give my baby formula automatically (even when she didn't need it) leading to problems with breastfeeding, and made them 'see' problems in the baby that she didn't even have. It led to a GREAT deal of unnecessary intervention. This is why critics charge that gd treatment can do more harm than good at times.
In subsequent pregnancies I tested negative for gd, despite being near 40. This may have been partly because the first diagnosis might have been wrong (due to the illness etc.), or it may have been because I made some big changes to diet and exercise the next two times, or a combination of both. In some ways the 'gd' was a gift because it helped me refocus my attention on cleaning up minor diet problems (I did not choose to diet, just became more careful about carb totals and junky food and increasing veggies and fruits), and it alerted me to watch for diabetes so if I get it I can catch it early before it does much damage. However, in other ways it was really unhelpful, since it labeled my pregnancy as high-risk unnecessarily, and probably led to my c-section. It also caused a great deal more fear and lack of confidence in myself in an already fearful pregnancy (from the other tests). The implications are also life-long; I was turned down in my third pregnancy for life insurance because of a past history of gd, even though I didn't have it afterwards and all other subsequent tests have been normal. This is ridiculous, but they stated it was because of the gd. The 'gd' label can follow you around for life.
If 'gd' really is a "diagnosis in search of a disease" (as some critics contend), and my borderline blood sugars really weren't a risk, I certainly paid a nasty price, and unnecessarily too. On the other hand, if even borderline blood sugars really are a risk and they can be helped by treatment (the jury is still out on this), then the screening and diagnosis was probably helpful in the long run. And I do have an early warning system in place for possible risk of full-blown diabetes in the future, which may help, but it has also added a great deal of worry and anxiety over that to my life as well. At this point, it's hard to tell whether the gd testing was really necessary and a good thing. However, it certainly was administered poorly, and I was not told how to take the test properly, which may have changed my results.
The point here is that not all providers agree on the value or reliability of the gd tests, so some women chose to take them and some women don't. Furthermore, the tests are not terribly reliable and can be affected by a number of outside influences like nicotine, illness, stress, etc. The screen test probably should not be taken right after a meal (wait 3 hours) so it does not measure both the meal carbs AND the test carbs. And different providers use different cutoffs for the 3 hour test, meaning that with same results you might get diagnosed with gd by one provider and not by another. In addition, women who get sick from the tests may want to explore the possibility of using an alternative form of test (see the gd testing section for more details). Some providers are open to the possibility of using other forms of testing instead.
There's a great deal of controversy over gestational diabetes in general, and in particular over the testing regimens used for it. Mothers would do well to research the issue more carefully before taking the test, and the GD: Testing section on this website may help you with this research. It also has numerous references for further exploration of the issue.
The Tentative Pregnancy: How Amniocentesis Changes the Experience of Motherhood. Barbara Katz Rothman. New York: W. W. Norton & Company, 1993. Available from www.birthworks.org or www.1cascade.com or www.amazon.com.
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 www.1cascade.com.
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.
Haddow, JE et al. Relation Between Maternal Weight and Serum Alpha-Fetoprotein Concentration During the Second Trimester. Clin Chem. January 1981. 27(1):133-4.
"Heavier pregnant women have lower median values, apparently as a result of a diluting effect of larger blood volume. This phenomenon is of clinical interest because alpha-fetoprotein concentration ...is one of the factors considered in assessing risk of poor outcome. A revision of the reference interval for alpha-fetoprotein to take body weight into account might improve its use as a diagnostic aid, especially in heavier women."
Wald, N et al. The Effect of Maternal Weight on Maternal Serum Alpha-Fetoprotein Levels. British Journal of Obstetrics and Gynaecology. November 1981. 88(11):1094-6.
"In 902 singleton pregnancies, maternal...AFP levels between 15 and 20 weeks of pregnancy were significantly related to maternal weight...Lighter women had on average higher AFP levels than heavier women, perhaps on account of the greater concentration of AFP in their relatively smaller volume of blood. The mean AFP level for women weighing less than 45 kg was 68% higher than the mean level for women weighing 85 kg or more. Maternal weight was found to be an important factor which could account for false positive AFP results in antenatal screening for open neural tube defects." Recommends adjusting AFP values according to maternal weight; estimates that the formula it recommends would have reduced the false positive rate in these 902 women screened from 2.8% to 2.0%.
Macri, JN et al. Maternal Serum Alpha-Fetoprotein Screening, Maternal Weight, and Detection Efficiency. American Journal of Obstetrics and Gynecology. October 1986. 155(4):758-60.
"Various methods of adjusting maternal serum alpha-fetoprotein levels based on maternal weight have been recommended in order to more appropriately assign risk in...screening. These adjustments may, however, result in a larger proportion of pregnancies designated as having increased risk and reduction in detection accuracy."
Drugan, A et al. The Inadequacy of the Current Correction for Maternal Weight in Maternal Serum Alpha-Fetoprotein Interpretation. Obstetrics and Gynecology. November 1989. 74(5):698-701.
"Correction for maternal weight compensates for the dilution effect of a larger plasma volume in women of greater weight." Analyzed the effect of a previously published linear correction formula for weight on a population of 8276 patients stratified by 50 lb. increments. "Without correction, the highest rate (15%) of low MSAFP results was obtained in the obese population. Conversely, the rate of elevated MSAFP was highest (3.8%) in the lowest maternal weight group. Correction for weight up to 250 lb significantly increased the rate of abnormally high results in the obese group, indicating an overcorrection effect." Suggests that linear correction of serum AFP results should be done only up to maternal weights of 200 lbs., and the women weighing more than this should be corrected only as if the weight were 200 lb to avoid over-correction yet still maintain the advantages of reduction in amnios found when weight correction formulas are used. (It is unknown whether this is still the rules used today or not.)
Neveux, LM et al. Refinements in Managing Maternal Weight Adjustment for Interpreting Prenatal Screening Results. Prenatal Diagnosis. December 1996. 16(12):1115-9.
Examines the relationship between maternal weight and the tests used for the Triple Screen more commonly used today (AFP, unconjugated estriol, and human chorionic gonadotropin) in 47,585 women. The large size of the study population gives sufficient numbers of women at the extremes of weight, and allows them to determine that a 'reciprocal-linear' equation more accurately describes the weight relationship for 2 of the 3 analytes than the currently used log-linear equations, but that the advantage is only minimal. However, it does note that the "published weight equations may not be optimal for some screening programmes, due to differences in the mean weight of the populations being tested. Screening programmes are encouraged to calculate their own weight correction formulae, based on data from their own population, and to monitor the mean maternal weight to detect when modifications in the weight correction formulae might be indicated."
*Numerous gestational diabetes references can be found in the websection on gd and gd testing on this website.
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