A case-control study of congenital hip dislocation.

In this study we have investigated various epidemiological factors which may be related to congenital dislocation of the hip (CDH). Eighty-one cases born during the period 1st January 1988 to 31st August 1990, with four matched controls per case, were identified from consultants' records held at the Queen's Medical Centre and City Hospital, Nottingham. One hundred and twenty-four subjects who were referred to a new Hip Instability Clinic with suspected CDH, but not diagnosed or treated for CDH, were also included as a third group. Information about the mother's pregnancy, previous medical history and family history was collected from obstetric records kept at the two hospitals. Multigravidae and similarly multiparous women had a statistically significantly reduced risk of having a baby with CDH. The relative risks were 0.55 (95% confidence interval 0.33, 0.93) and 0.53 (95% confidence interval 0.31, 0.91) respectively. The method of delivery was also of importance. Babies born by Caesarean section or in breech position had an increased risk of CDH which was statistically significant. Using addition clinical information obtained from subjects attending the Hip Instability Clinic we also found that cases were more likely to have a family history of CDH than subjects who were screened for CDH but found to be normal.