Dietary folate and nonneural midline birth defects: no evidence of an association from a case-control study in Western Australia.

In a population-based case-control study of dietary folate and neural tube defects, information was collected by interview and self-administered questionnaires from the mothers of cases with only neural tube defects, from the mothers of matched control infants with defects other than neural tube defects, and from the mothers of matched live-born infants with no birth defects. The association of midline birth defects (excluding neural tube defects) with dietary folate intake in the first 6 weeks of pregnancy was assessed by restricting the analysis to the 59 mothers of infants with midline defects in the first control group and comparing them with their matched control infants in the second control group. The crude and adjusted odds ratios for dietary folate and for folic acid supplementation were close to one, and all confidence intervals embraced unity. These data do not provide evidence of an association between midline birth defects (excluding neural tube defects) and either dietary folate or folic acid supplementation.