Maternal serum α-fetoprotein in the first trimester cannot predict neural tube defects

We tried to establish the norm (mean, median, and MOM) for first-trimester (9-12 weeks' gestation) MSAFP and AFAFP. During this study, we found three cases of NTDs at 11-12 weeks-two cases of acrania and one case of meningomyelocele. In all three cases, the MSAFP levels were within the normal range, while the results for AFAFP in the NTD cases were very high. Thus, the lack of correlation between MSAFP and AFAFP together with our findings of high AFAFP in combination with the normal results of MSAFP in the NTD cases leads to two conclusions: (1) MSAFP cannot predict AFAFP and its use is precluded in the first trimester as a screening tool for detecting NTD; (2) NTDs can be diagnosed in the first trimester, though only by detecting the AFP in the amniotic fluid via early amniocentesis. (DBO)