The association between mode of delivery and developmental dysplasia of the hip in breech infants: a systematic review of 9 cohort studies.

Although developmental dysplasia of the hip (DDH) is a relatively common disorder, its aetiology remains elusive. The authors undertook a systematic review to determine whether there is an association between DDH and vaginal or caesarean delivery for singleton breech infants. The review focussed on cohort studies which provided risk estimates for DDH in breech-presenting infants, as a function of mode of delivery. Nine cohort studies with 35,139 infants were found. In the short-term, breech infants delivered through caesarean section had a significantly lower risk (13.5% less) for DDH: 5.95%, versus 6.88% (weighted values) in the vaginal delivery group (p = 0.008) {RR = 0.87 (95% CI 0.78-0.97)}. This might be mediated by the reduced stretch of the hip capsule, due to the absence of increased uterine pressure, which normally occurs in the active phase of labour. This pleads for the hypothesis that the mode of delivery is the critical factor promoting dislocation, not the breech presentation itself. Long-term data were not available, so that the overall effectiveness of caesarean section compared to vaginal delivery could not be established.