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 α‐thalassaemia‐1 or β‐thalassaemia heterozygotes. α‐ and β‐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 α‐thalassaemia‐1 heterozygotes, 102 women were β‐thalassaemia heterozygotes and one woman had HbE disease. Three α‐thalassaemia carriers and one β‐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 α‐ and β‐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. Copyright © 1999 John Wiley & Sons, Ltd.

The prevalence and spectrum of α and β thalassaemia in Guangdong Province: implications for the future health burden and population screening

“…This raises practical issues when using haematological tests as the screening methodology because there are no significant haematological differences between coinherited a and b thalassaemia and b thalassaemia 2 ; this was confirmed by the results of our haematological analysis of these 20 samples (data not shown), although MCV and a to b ratio values may be raised to varying degrees in coinherited a and b thalassaemia. To prevent concordant a or b thalassaemia heterozygotes from escaping detection, as has been reported for b thalassaemia carriers in Hong Kong, 31 we suggest that a thalassaemia mutations should be screened for in all b thalassaemia couples in the Guangdong area. This will allow us to offer comprehensive genetic counselling to those couples with a or b thalassaemia who are concordant and discordant heterozygotes.…”

Hemoglobin H disease: not necessarily a benign disorder

“…There is a suggestion that the risk of fetal neural tube defect is increased in pregnant women who are either ␣-or ␤-thalassemia carriers, possibly because of relative folic acid deficiency secondary to increased erythropoiesis. 126 For pregnant women with Hb H disease, it is especially prudent to prescribe folic acid supplement during the periconceptional period and beyond.…”

Guideline for the Management of Conception and Pregnancy in Thalassaemia Syndromes: A British Society for Haematology Guideline

“…Preconceptual high-dose folic acid (5 mg daily) starting 3 months prior to conception reduces the risk of neural tube defects 78,79 and should be continued throughout pregnancy. Currently, UK guidelines recommend that splenectomised patients with thalassaemia syndromes require penicillin prophylaxis as they are susceptible to infection by encapsulated bacteria [80][81][82] for example Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae type b.…”