During a second trimester serum screen for fetal spina bifida, a patient may have an elevated maternal serum Alpha-Fetoprotein (AFP, or MSAFP) level. Elevated MSAFP is associated with structural fetal anomalies, including neural tube defects, abdominal wall defects, and duodenal atresia. With targeted ultrasounds, abnormalities of the spine, brain, or abdominal wall should be apparent. Therefore, for women with an elevated MSAFP and a normal ultrasound, the likelihood of a major structural anomaly should be very low.
Workup for Elevated MSAFP
In the past, amniocentesis was performed routinely in the setting of an elevated MSAFP in order to test amniotic fluid AFP and acetylcholinesterase (AChE) levels. If these levels are normal, the likelihood of a fetal structural defect was significantly lower.
Although amniocentesis remains an option, recent data suggests that in experienced centers, a targeted ultrasound is as sensitive and specific as amniotic fluid AFP and AChE levels. In the setting of very high MSAFP levels, an amniocentesis could help rule out congenital fetal nephrosis, which is a rare and usually lethal disorder.
In the setting of an unexplained elevated MSAFP, the biologic explanation is usually a breech of the maternal-fetal interface at the placenta, and these pregnancies can be at an increased risk for placental abruption, preeclampsia, fetal growth restriction, fetal death, and preterm birth.
If the targeted ultrasound shows no evidence of abnormalities of the spine, brain, or abdominal wall, serial growth ultrasounds are recommended. If the fetal growth is normal, outcomes are usually normal.
Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!