First-trimester screening for neural tube defects using alpha-fetoprotein.

OBJECTIVE To assess the potential value of maternal serum alpha-fetoprotein (AFP) at 11-13 weeks' gestation in early screening for fetal neural tube defects (NTDs). METHODS Maternal serum AFP at 11-13 weeks' gestation was measured in 32 cases of fetal NTDs, including 18 cases of acrania and 14 cases of spina bifida, and 1,500 unaffected controls. The measured serum AFP was converted into multiple of the expected median (MoM) after adjustment for gestational age and maternal characteristics and Mann-Whitney test was used to determine the significance of difference in the mean MoM of serum AFP in the NTD group to that in the controls. RESULTS The mean AFP MoM in the NTD group (1.76, 95% CI 1.39-2.23) was significantly higher than in the controls (p < 0.0001). The mean AFP MoM was not significantly different between the cases of acrania and cases of spina bifida (1.78 vs. 1.75; p = 0.722). The detection rates of NTD in screening by serum AFP were 50.0% (95% CI 31.9-68.1) and 37.5% (95% CI 21.1-56.3) at fixed false-positive rates of 10 and 5%, respectively. CONCLUSION Measurement of maternal serum AFP at 11-13 weeks' gestation may be useful in screening for fetal NTDs.