[Epidemiology of polydactylies: a case-control study in the population of Pelotas-RS]

OBJECTIVE: To identify and compare cases of isolated polydactyly with healthy newborns regarding familial and maternal characteristics. METHODS: We conducted this hospital-based case-control study from 1990 to 1998. We collected data in interviews with mothers of cases and controls during the post-delivery period. Cases were defined as newborns presenting an extra or a bifid digit in hands and/or feet. Controls were the four healthy newborns that were born after the case, at the same hospital. Information was gathered on type of polydactyly, gender and birthweight, twin pregnancy, parental consanguinity, ethnicity. RESULTS: African ancestry and positive family history of congenital malformation, especially polydactyly, were significantly associated with the occurrence of this type of congenital anomaly (crude OR of 3.3; 10.0; and 55.0, respectively). CONCLUSION: Isolated polydactyly was one of the most frequent malformations found in the studied population. The findings associated with black African ancestry confirm the data presented in the literature. Studies conducted on this same population, with a larger population of patients with this type of malformation, could investigate this association better and justify the results presented here.