Maternal drinking and smoking and the risk of birth defects

: Maternal drinking or smoking and the risk of birth defects was studied in a case-control study, performed on 1,789 babies, born between 1990 and 1992 in the Tokai University hospital, and their mothers. The findings were as follows: The proportion of maternal drinking before or during pregnancy was higher in the mothers of children with birth defects (odds ratio 2.2; 95% confidence intervals 0.5-8.9). However, this difference was not statistically significant. Maternal smoking, defined as 11 or more cigarettes per day before pregnancy, was 13.5% in the mothers of children with birth defects, compared to 6.7% in the mothers of controls (odds ratio 2.2; 95% CI 0.6-7.4). This difference was not statistically significant. A total of 78 classified deformities were reported in the 52 children with birth defects, of which 24.4% were associated with maternal drinking and 16.7% were associated with maternal smoking, respectively. A significant association was found between premature birth and mothers who reported drinking during pregnancy (odds ratio 3.3 95% CI 1.1-10.9). The frequency of spontaneous abortion was higher among mothers who reported both drinking and smoking during pregnancy. In addition the frequency of complications during pregnancy was higher. Analysis of factors related to birth defects showed that the risk for birth defective infants was higher for mothers above 35 years of age than for those under 35 (p < 0.05). This study supports an association between maternal drinking during pregnancy and infant birth defects, but does not implicate maternal smoking because the number of mothers who smoked during pregnancy was too small to be of significance.