The most misunderstood pregnancy test and why you might want it
Apr 7, 2000
If you are pregnant or planning on becoming pregnant, you can expect to be offered the Maternal Serum Alphfetoprotein (MSAFP). You can also expect many women (and even some physicians) to try and discourage you from having this test done. You'll hear about all the "false positives" of this test.So, if so many people are against this test, why is it even around? This is a newer test (only been around since the 1980's) and many people remained uninformed of everything abnormal test results can indicate. Also, much research is still being done on this screening, so we do not yet know all that this test can find, but we are learning. So, while you may have an abnormal test result and your baby may be born with no birth defects, this does not indicate a "false positive". Your test was most likely abnormal for a reason whether it be an inaccurate due date, placental problems, increased risk of stillbirth, or a myriad of other reasons and often you may never find out what the reason was.
What is the MSAFP?
The MSAFP is currently an optional blood test given between the 16th and 18th weeks of pregnancy. I say "currently" because I do believe that in the future, this will be given to all women once all the benefits of this test become more widely recognized. Currently, a pregnant woman can opt not to take the test and many do. This blood test is offered as a way to better accurately predict not only chromosomal abnormalities and birth defects, but can also be an indicator of future pregnancy-related problems. As with any concern during your pregnancy, you should talk to your OB-GYN, but I'd like to give you a little info on this test before you do.
What is the AFP?
The alphafetal protein (AFP) is actually a protein made by the baby and is excreted into the amniotic fluid and mother's bloodstream. The test which actually screens for three things. The triple screen includes the AFP, estrogen (estriol)level and hCG level. Along with these three screening, race, age, and weight are factored into the calculation. Each of these three levels will come back either normal, high, or low and from there, specialists can determine for what your baby may be most at risk.
This test will have abnormal results in approximately 65% of babies with Down Syndrome. The levels will be significantly elevated in more than 90% of babies with brain, spinal cord, or abdominal wall defects. The current rates are 95% of anencephaly cases, 80% of Spina Bifida cases, and 60% of Down syndrome cases.
Does this mean that if you have elevated levels you have a 90% chance of having a baby with one of these defects? NO, it does not. It means that if your baby does have the defect, the test will catch it over 90% of the time. On the flip side of the coin, having a test come back normal does not guarantee that your baby will not have any defects. This test just gives you a better idea whether your baby or pregnancy is at higher risk. I cannot emphasize enough that just because this test may come back positive, this does not mean a problem has or will occur, but it might and it is always safer for your baby to be prepared.
Chance of this test having an abnormal result
Out of every 1,000 women who take this test, approximately 100 will have abnormal results. This means that 900 women have normal results and now know they have a lessened chance of a birth defect (not completely ruled out, but lessened quite a bit). Out of the 100 women who had abnormal results, approximately 3% will have a baby with a birth defect or chromosomal abnormality. The majority of the other 97% of abnormal results will just be because the pregnancy is either further or not as far along as thought or there might be some complications with the pregnancy itself.
High levels of the AFP (particularly the hCG portion) can be markers for conditions such as Spina Bifida, abdominal defects, Anencephaly which is a neural tube defect, other neural tube defects, multiple babies, pregnancy-induced hypertension, or death of baby. While a positive AFP score does not necessarily mean a genetic defect, it can be a marker for problems occurring in the third trimester. Some of those problems may be placental abruption or other placental problems, low birthweight, low amniotic fluid levels, preterm labor, and risk of stillbirth. These risks are much more likely in women with abnormal AFP tests, but the risk is still quite low.
These levels may indicate Down Syndrome (DS) and other chromosomal defects. By the way, the levels are low for the AFP and estriol portions of the test, but high for the hCG. So if your hCG level is high, please read the above paragraph for other possibilities. Approximately 1 in 800 babies born has DS however the majority of babies with DS are aborted so that number is actually much higher for babies in-utero with DS. Heart defects and varying levels of mental retardation are common in children with DS, so by being made aware your baby could possibly have DS, your hospital will be better prepared to deal with these defects at birth. Yes, the possibility of having a baby with DS increases with age especially once you are over 35, but the majority of babies born with DS are to mothers under 35.
My test is positive what happens next?
Depending on your state of residence, you may meet with a geneticist who will go over all your possibilities with you and tell you what you may expect. You'll find out your chances of having a baby with one of these defects. However, as of yet, they are unable to tell you the possibility of having a pregnancy-related problem during your pregnancy, but this is still so new. They have a ways to go with the study. They will most likely schedule you for an ultrasound (usually level II) in which they'll really examine the baby and take a number of measurements. You may also be asked to take an amniocentesis to confirm a chromosomal abnormality. After these test results are received, your physician and you will discuss what happens next and as I have found out, this varies from doctor to doctor.
A tale of three friends
When my screening results came back positive at seventeen weeks, I was promptly given an appointment with a geneticist. I was given the option of additional tests (level II ultrasound and amniocentesis). I was also given the option of aborting my baby. My husband and I were absolutely not interested in the abortion, so instead, we quizzed our geneticist and physician about everything this could mean (this is where I learned about everything the test was capable of picking up). We had the level II ultrasound and our chances of having a baby with DS became even greater. I turned down the amnio because my risk of miscarrying with the amnio would be 1 in 200 (definitely not worth it for me). Through an online support network, I befriended two other women whose tests came back abnormal around the same time and they were due around the same time. Only difference among the three of us was my doctor made me high-risk, made me quit work, and made me take it easy. The other doctors just mentioned the "high rate of failure" with the AFP and these women continued on at their jobs and took no added precautions. I am sad to say that both women lost their babies. My son was born without Down Syndrome, but as it turns out my placenta had had a "stroke" and was partially dead. Also, the umbilical cord was not fully attached. Was this why my triple screen came back positive? My doctor tends to believe so. Had I continued working and not taken the added precautions after my abnormal AFP, my son might have joined those other two babies in Heaven.
So why is this test a good thing?
Ninety percent of all women are going to get back normal results. This means peace of mind (at least a little more of it) for these women. If the test results are abnormal for those other 10% of women, their doctors can take the necessary steps to rule out various defects and take an extra interest in the progression of their pregnancy. Often doctors who are aware of the additional information this screening can provide will deem your pregnancy to be high risk which may result in saving your baby's life. You will also be giving your hospital the advantage in knowing what preparations need to be made (i.e. surgery when baby is born, specialized equipment, etc...). By allowing this test to be done, you may be made aware of potential problems and your doctor can act accordingly.
The last thing I want to do is worry you if you've had an abnormal triple screen. I know that once armed with this information however, worry just cannot be avoided. Believe me, I remember all too well how I worried and how many sleepless nights I spent. But, let me remind you, my son is here today and there is a good possibility he might not be without this particular test. I'm not a doctor nor do I play one on TV, but I just want to caution you to take the information you've learned here to your physician and discuss the possibility of more than just a baby with a chromosomal defect. If you have an abnormal result, do proceed a little more cautiously with your pregnancy, your baby's life may be depending on it.