What does a lower-than-normal MSAFP level warrant a follow-up for?

A lower-than-normal level of maternal serum alpha-fetoprotein (MSAFP) is primarily associated with an increased risk of certain chromosomal abnormalities, particularly Down syndrome (trisomy 21). MSAFP is a protein produced by the fetal liver, and its levels are measured during the second trimester as part of routine prenatal screening. While low MSAFP levels can indicate possible concerns regarding fetal development, they are particularly correlated with an increased risk for Down syndrome.

In assessing the options, neural tube defects are more typically associated with elevated MSAFP levels, while the fetal position and placental abnormalities are not directly linked to MSAFP levels in the same manner. Therefore, the correct follow-up for a lower-than-normal MSAFP level is an evaluation of the risk for Down syndrome, highlighting the importance of this test in prenatal screening protocols. Further diagnostic testing, such as an ultrasound or amniocentesis, may be recommended to clarify the risk and ensure appropriate monitoring and care.