A study of neural tube defects in a South African population
Neural tube defects are a common cause of morbidity and mortality in the South African population and occur in about 1 in 800 births. They are usually multifactorial in aetioloyy and this study analysed some of the possible risk factors, both environmental and genetic, in an attempt to establish their relative importance to the occurrence of neural tube defects in the population of Gauteng. A retrospective study was undertaken using 640 files of patients with neural tube defects seen at the Genetic Counselling Clinics of the Department of Human Genetics, University of the Witwatersrand and School of Pathology, South African Institute for Medical Research. The study showed that while maternal age was not a significant risk factor for the occurrence of neural tube defects, maternal parity did play a role. In addition, a history of spontaneous abortions and congenital malformations in other offspring seemed to increase a couple’s risk of having a subsequent pregnancy affected by a neural tube defect. Maternal factors such as diet and teratogen exposure during pregnancy were also shown to be important risk factors. Correlations could not be demonstrated between season of birth, social class or history of twinning and the occurrence of neural tube defects. The study also attempted to determine the recurrence risks of neural tube defects in the population and the sex ratios of affected individuals. A recurrence risk of 2.28% was calculated for neural tube defects following the birth of one affected child and significantly more females were shown to be a fleeted by these disorders. In addition, a molecular analysis was undertaken to determine the contribution of the 677C-T mutation in the methylenetetrahydrofolate reductase gene to the aetiology of neural tube defects in the black population of Gauteng. The mutation was shown to occur significantly more frequently in the Caucasoid than in the Negroid population uf Gauteng. The occurrence of the mutation was not shown to be significantly different in the small sample of black women tested who had had pregnancies complicated by neural tube defects than in the general population from which they were drawn. The study also undertook to ascertain some of the psychosocial issues surrounding the birth of a child with a neural tube defect in the black population of South Africa. Interviews were performed with black women who had had affected pregnancies and the findings were compared to matched controls from the same population. The results indicated that awareness of and understanding of the aetiology of neural tube defects is low in this population. The results indicated however that there was a willingness to undergo prenatal diagnosis and termination of affected pregnancies in both the experimental and control groups interviewed. Significantly more women who had had children with neural tube defects were shown to suffer from depression than women from the matched control group.