[Etiologic and epidemiologic aspects of neural tube defects]

A case-control study of neural tube defects (NTD) was undertaken from 1979 to 1986 in the department of Bas-Rhin in Northeastern France. For 105,374 consecutive births the incidence of spina bifida was 0.62 in 1,000, the incidence of anencephaly was 0.33 in 1,000 and that of encephalocele was 0.14 in 1,000. Sex ratios were respectively 1.06, 0.64 and 0.75. Among the numerous etiological factors which were studied we observed a seasonal factor (more conceptions in April, less in September). Birth weight and length were lower in children with spina bifida than in controls. Metrorrhagia was more frequent during pregnancies with anencephaly as was oligoamnios in pregnancies with encephalocele. Routine US prenatal diagnosis, which was performed in 90% of the pregnant women, allowed diagnoses in 88% of the fetuses with anencephaly but only in 53% of the fetuses with spina bifida and in 64% of the fetuses with encephalocele. For these last two anomalies diagnosis could often be performed because a malformation was associated with a NTD.