Measuring alpha-fetoprotein (AFP) level by a blood test checks for a birth defect known as spina bifida (open spine deformity). One out of every 1,000 babies in the United States is born with this defect. About 80 percent of the time when a woman is carrying a child with spina bifida, her blood test will show a higher than normal AFP level.
- Should I have this test if there has never been anyone in our families with spina bifida?
In 90 to 95 percent of the cases in which a child is born with spina bifida, there has never been anyone else in the family with this problem. We are not able to predict which pregnant women, who do not have a relative with spina bifida, may give birth to a child with this defect.
- What if my partner or I have a relative with spina bifida?
A family history of spina bifida or other spinal cord problems may indicate a higher than expected risk. Our genetic counselors can help determine what your risk is and what type of test would be best for your situation.
- If my blood test shows a high level of AFP, does that mean that my child will have spina bifida?
No, not necessarily. There are many other reasons why the AFP level may be higher than normal in a woman's blood. In fact, most women with a higher than expected level of AFP will have normal babies. Sometimes the AFP blood test may be repeated and this result may show a normal level. An ultrasound often explains why the AFP level is high. For example, the pregnancy may be further along than realized, or the woman may be carrying twins.
- What if my blood test shows a high level of AFP and the ultrasound does not show a reason for this: does this mean spina bifida?
No, not necessarily. Once again, most women in this situation have normal pregnancies. However, an amniocentesis may be suggested, since this is a very accurate way to determine if the fetus has spina bifida. Amniocentesis is a test done by taking a small amount of amniotic fluid (water around the fetus) and measuring the AFP in the fluid. Alternatively, patients with elevated blood AFP levels that are unexplained have an increased risk for complications later in pregnancy and are watched more carefully by their doctors in the third trimester.
- What if you find that my baby has spina bifida or some other birth defect?
In cases such as this, our genetics staff will help explain the results of the test as well as discuss all possible options with you, including delivery and raising a child with special needs.
- What if my blood test is normal? Does that mean that the baby will be normal?
No, not necessarily. Most birth defects do not cause a high AFP level. Even some women who are carrying a child with spina bifida have a normal level of AFP. However, a normal result implies that you are not at an increased risk for an open spine deformity and a variety of other fetal problems.
Penn Ob/Gyn Care physicians and counselors provide prenatal diagnosis, consultation and care at various locations throughout the Philadelphia region. Please call 800-789-PENN (7366) for more information.