What is AFP?

I am a 29-year-old woman, 14 weeks pregnant with my second child. I had an ultrasound at eight weeks, and all appeared normal. My OB suggested an MSAFP test at my next appointment, but I am not in any of the normal risk categories. Given the high rate of false positives, do you suggest this test be performed routinely?

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Peg Plumbo CNM

Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more

I understand your concern, and you have every right to decline this test. It is very important, however, that your care provider explain this test to you -- and to every pregnant woman -- not necessarily to convince you to have it, but to inform you.

The AFP test is a screening test only, and all higher- or lower-than-expected levels should be checked out with ultrasound and/or amniocentesis.

The risk of having a baby with a neural tube defect is about one in 1,000. There is a spectrum of defects associated with an open neural tube -- from insignificant to anencephaly or intrauterine fetal death. Because this test is so good at picking up this particular defect (and also Down Syndrome, although not as well), it must be offered to all expectant couples.

As there is no treatment for this defect, knowing is a matter of preparation; in some cases, a second-trimester abortion may be considered.

Only about five percent of tested women will have an elevated AFP, and if you are dealing with very good dates and can zero in on the 15 to 20 week gestations, the positive rate goes to three percent. This is not really very high, and an ultrasound can help lower the false positives even farther.

I always tell parents it is very much up to them, and they should consider if they would like to (or need to) know in order to prepare or consider abortion.

I hope this has helped a bit, and good luck with your decision.

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