Maternal plasma alpha-fetoprotein screening for fetal neural tube defects.

Maternal plasma alpha-fetoprotein (AFP) screening for fetal neural tube defects (NTD) was used as a part of routine antenatal care in three hospitals over a 26 month period. Blood samples were obtained for plasma AFP measurement at 15 to 20 weeks gestation from 6377 women, representing 79 per cent of antenatal bookings. The outcome of pregnancy was ascertained in 96 per cent of patients: 13 cases of anencephaly and 7 of open spina bifida were detected by plasma screening and a further 3 cases of open NTD through the mother's previous medical history and amniotic fluid determination. Four fetuses with open NTDs and four with closed NTDS were not detected by plasma AFP measurement and the detection efficiency for open NTDs was thus 83 per cent. Integration of screening into the existing pattern of antenatal care required only minor alterations in clinic schedules. Some extra time was needed for explanation of the objectives of the study, for ultrasound examination and for amniocentesis. Eight patients declined the offer of a plasma test, while only one refused an amniocentesis.