Maternal smoking and anencephaly

Abstract

In 1979 Evans, Newcombe, and Campbell published a valuable analysis of the Cardiff Birth Survey, showing little association between maternal smoking in pregnancy and most types of those congenital defects which are recognised neonatally. They did, however, find a weak association with anencephaly (132 cases) and spina bifida (178 cases), even after controlling for social class. We present an analysis of 491 pregnancies resulting in the birth of a singleton anencephalic. The available evidence suggests that although maternal smoking is demonstrably associated with reduced birth weight and perinatal loss, there is little to suggest that major malformations of the central nervous system are associated with the habit. This is relevant in the current debate on the efficacy of multivitamin supplements given before conception to women who have had an infant affected with anencephaly or spina bifida, since smokers are known to have low serum vitamin C concentrations. Evidence from our study therefore suggests that lack of this particular vitamin was not of importance in the aetiology of anencephaly.