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.