RESUMO
PURPOSE: To ascertain the presence of recall or report bias in a case-control study on congenital dysplasia of the hip (CDH). METHODS: A hospital case-control study was performed. Those cases and controls with other malformations or from mothers with clinical problems were discarded. 97 cases of dysplasia, and 164 controls were collected. Mother's life style was assessed. Odds ratios (OR) (crude and multiple-factor adjusted by logistic regression analysis) and their 95% confidence intervals were estimated. Risk factors were analyzed stratifying by the results of Ortolani-Barlow maneuver, since women were interviewed after knowing these results. RESULTS: Mothers of newborns with a positive Ortolani-Barlow maneuver yielded a higher OR for positive family history than those of babies with a negative one (2.27 versus 1.38). Overall smoking and alcohol consumption, and number of health exams during pregnancy yielded a negative association with CDH. In these cases closer-to-the-null ORs were obtained in newborns with positive Ortolani-Barlow. CONCLUSIONS: The presence of a report or recall bias is suggested as one of the possibilities for explaining the results.