EXPERIENCE WITH α-FETOPROTEIN (AFP) IN PRENATAL DIAGNOSIS OF NEURAL TUBE DEFECTS (NTD)

Abstract

The use of AFP assays of amniotic fluid (AF) as a diagnostic adjunct to the prenatal diagnosis of these defects represents the most significant advance yet in prevention through early detection. AFP assays by electroimmunodiffusion were done on AF's derived from 525 cases (10-34 weeks gestation) with subsequent normal births. The observed normal range of AFP ± 2 S.D. is shown in the table. A narrow normal range of

AFP concentration is evident. Additional assays were done on AF's in cases with fetal abnormalities (24), fetal death (8) and obstetric complications (9). A slight elevation in AFP concentration was noted in 1 fetus with Turner's syndrome. In studies prior to 20 weeks gestation 2 fetuses with anencephaly and 1 with spina bifida were detected. A striking fall in AFP concentration (16.5 to 4.55 mg%) was observed between 16 to 21 weeks in 1 case of anencephaly. In the overall total of 577 cases, 43 were mothers who had previously had an affected child with a NTD. No elevated AFP levels were found in this group. About 90% of all NTD's may be diagnosable through AFP assay between 14-18 weeks gestation.

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