Preaxial polydactyly of feet in infants of diabetic mothers: epidemiological test of a clinical hypothesis.

Using data from the Spanish Collaborative Study of Congenital Malformations (ECEMC), we tested the hypothesis of Carey et al. (Proc Greenwood Genet Cent 9:95, (1990) on maternal diabetes and preaxial polydactyly of feet in infants born to diabetic mothers. Our results seem to confirm their suggestion, although the hallucal type of preaxial polydactyly that they described seems to be much less frequent. Nevertheless, a high risk exists (OR = 24.60, P = 0.0004) for preaxial polydactyly of the feet in relation with other types of birth defects or postaxial polydactyly. This analysis shows the importance of clinical observations for epidemiologists, because such observations constitute hypotheses and provide actual issues for study, and clinicians will get epidemiological confirmation for their individual observations and hypotheses.