Use of folic acid supplements and risk of cleft lip and palate in infants: a population-based cohort study.

BACKGROUND Orofacial clefts occur when the lips or the roof of the mouth do not fuse properly during the early weeks of pregnancy. There is strong evidence that periconceptional use of folic acid can prevent neural tube defects but its effect on oral clefts has generated debate. AIM To identify factors associated with suboptimal periconceptional use of folic acid and its potential effect on oral clefts. DESIGN AND SETTING The population-based infant cohort of the national Growing Up in Ireland study, which consists of 11 134 9-month-old infants. METHOD Data collection comprised questionnaires conducted by interviewers with parents in parents' homes. Characteristics of mothers who did or did not take folic acid before and during pregnancy, as well as the effect of folic acid use on the prevalence of cleft lip and palate were recorded. RESULTS The prevalence of cleft lip and palate was 1.98 (95% confidence interval [CI] = 1.31 to 2.99) per 1000 9-month-olds. The odds ratio for cleft lip was 4.36-fold higher (95% CI = 1.55 to 12.30, P = 0.005) for infants of mothers who did not take folic acid during the first 3 months of pregnancy, when compared with those who did have a folate intake during the first trimester. Folic acid use was suboptimal in 36.3% (95% CI = 35.4 to 37.2) of the sample. CONCLUSION These findings support the hypothesis that taking folic acid may partially prevent cleft lip and palate. They are particularly relevant for GPs, because they are usually the first port of call for women before and during early pregnancy.