AVOIDANCE OF ANENCEPHALIC AND SPINA BIFIDA BIRTHS BY MATERNAL SERUM-ALPHAFETOPROTEIN SCREENING

Abstract Screening of 11 585 pregnant women between 16 and 20 completed weeks' gestation for raised serum-alphafetoprotein (A.F.P.) levels showed that the birth of 81·4% of babies with open neural-tube defects could be avoided. The screening test was sensitive enough to detect 93% of those affected and serum-A.F.P. levels above the point at which intervention should be considered were found in 1·7% of pregnancies. After 75·2% of false-positives had been excluded by ultrasonography or by a repeat of the serum test, only 0·63% of pregnancies proceeded to amniocentesis. 46·6% of amniocenteses showed raised amniotic A.F.P. levels due to fetal abnormality. Fetal loss by abortion or perinatal death after amniocentesis occurred in 0·034% of pregnancies screened, 75% being associated with threatened abortion before amniocentesis. There were no terminations of normal pregnancies due to false-positive amniotic A.F.P. results. It is concluded that voluntary maternal serum-A.F.P. screening has a valuable role in antenatal care.