Can you explain how the MSAFP test works?
MSAFP testing confuses lots of people! The MSAFP test is a screening test, not a diagnostic test. It tells us only that there's a possibility of a problem, not that there really is a problem.
MSAFP is a substance made by the fetus that shows up in the mother's blood. If there's too much MSAFP in the mother's blood, it could mean that the baby
has something like spina bifida. If there's not enough MSAFP in the mother's blood, it could mean that the baby
has Down's syndrome. The MSAFP test can only be done at a certain time in pregnancy
(between 14 and 19 weeks).
It's a good test, but not foolproof. First, the woman has to be sure about when she became pregnant. Second, the results are dependent on whether she's having one baby
, twins, or more. There are other things that can make the test results seem wrong as well. Even when a woman is sure of her dates, in about 5 percent to 8 percent of cases the result comes back positive, but the baby
has no problem. That's why, when a test comes back positive, the doctor will often repeat the test or do an amniocentesis (taking some amniotic fluid out of the uterus) to really find out what's happening. An amniocentesis is a diagnostic test, meaning that a real diagnosis can be made based on the results. I hope this helps you understand this test better.