Risk of neural tube defects in the offspring of thalassaemia carriers in Hong Kong Chinese

Abstract

The risk of having an offspring with neural tube defect is negatively correlated with early pregnancy maternal folate levels. Thalassaemia carriers often have subnormal folate levels. We postulate that their offspring may be at increased risk of having neural tube defect. We retrospectively reviewed the records of 1961 Chinese women referred to a tertiary centre for prenatal diagnosis between January 1997 and August 1998. Women with a mean corpuscular volume greater than 80 fl were assumed not to be alpha-thalassaemia-1 or beta-thalassaemia heterozygotes. alpha- and beta-thalassaemia heterozygotes were diagnosed by haemoglobin studies. Of the 1961 women studied, pregnancy outcome was not available in 20 and thalassaemia screening was not available in 109 and these were excluded from the final analysis. Two-hundred-and-six women were alpha-thalassaemia-1 heterozygotes, 102 women were beta-thalassaemia heterozygotes and one woman had HbE disease. Three alpha-thalassaemia carriers and one beta-thalassaemia carrier had a pregnancy affected by anencephaly (odds=1:76). In the 1523 non-carriers, five pregnancies were affected by spina bifida (odds=1:304). The odds ratio (95 per cent confidence interval) for neural tube defects in the alpha- and beta-thalassaemia carriers was 3.99 (1.07 to 14.94; p<0.05, Chi-square test). Because of the small number of affected pregnancies studied, the finding needs to be substantiated by a larger series. If the increased risk is genuine, women need to be screened for thalassaemia before conception and the thalassaemia carriers should be given periconceptional folate supplement to reduce the occurrence of neural tube defects.