Neural tube defects in Gauteng, South Africa: recurrence risks and associated factors.

BACKGROUND After congenital heart disease, neural tube defects (NTDs) are the most common serious structural birth defects in human infants. OBJECTIVES To (i) determine the recurrence risks of NTDs in the population of Gauteng; (ii) investigate some of the risk factors shown to be important in the occurrence of NTDs in other populations; and (iii) determine their relative importance in the aetiology of NTDs in the Gauteng population. METHODS A retrospective study was undertaken of 640 families with a member with an NTD. Data were collected from the genetic counselling files held in the Department of Human Genetics for a 28-year period. RESULTS A recurrence risk ± standard deviation (SD) for NTDs of 2.28±0.9% (1/45) was calculated for the population. There was no significant difference between the risk of recurrence 0.73±1.0% for the black families (n=98) compared with those for the total sample (N=621). The risk rose to 4.16% after giving birth to two affected children. Analysis of the gender of those with NTDs showed that significantly more female infants (male:female ratio 0.82) were affected. The study also showed that while maternal age was not a significant risk factor for the occurrence of NTDs, maternal parity did play a role, and first and last children were at increased risk. In addition, a higher occurrence of spontaneous abortions and of apparently unrelated congenital malformations in other offspring was found in families with a child with an NTD. CONCLUSIONS This study provides unique information relevant to the genetic counselling of families with a member with an NTD in our population. All affected families should be referred to a genetics service for appropriate counselling.