Prenatal screening for neural tube defects in South Africa. An assessment.

Neural tube defects (NTDs) occur in at least 1 in every 1000 babies born in South Africa. The incidence is uncertain but appears to be highest in Whites and Coloureds and lowest in Blacks. Spina bifida is a particularly serious problem because many affected babies survive and require extensive, costly treatment and care. A high maternal serum alpha-fetoprotein (AFP) level may indicate that the fetus has an NTD. Enzyme-linked immunosorbent assay is well suited to mass screening of maternal sera. The Natal population is used as a model here, and it is calculated that of some 122000 pregnancies annually 38725 might be screened. Of 98 expected fetuses with an NTD, 32 (16 with anencephaly and 16 with spina bifida) should be detected. If the 16 fetuses with spina bifida were not detected and those pregnancies terminated, the cost of caring for the affected children through their first decade is conservatively estimated at R145660, an average of R9 100 per patient; 92% of this would be incurred in the first 3 years. The cost of screening, at R2,27 per subject, is calculated to be R87 825, equivalent to R2 744 per fetus with an NTD detected or R5 489 per fetus with spina bifida detected. Financially the introduction of mass screening of maternal serum AFP is justified, but before this can be done adequate ultrasound facilities must be provided and a permanent health visitor must be available to trace women at risk and arrange their further investigations. A public education campaign should also be introduced. Some ethical and legal implications of mass screening for NTDs are discussed briefly.