Breech presentation is historically associated with an increased incidence of hip Dysplasia (6.6%–9.6%), but the effect of vaginal breech delivery on the development of hip dysplasia is unknown. In the Irish Republic, the proportion of breech presentations delivered by caesarean section is now over 90%. If the mechanical trauma of vaginal delivery is a significant event in the aetiology of DDH in breech presenters, caesarean section should be protective. We tested this hypothesis by a prospective study in infants presenting in the breech position who were delivered by caesarean section, during the 2002 calendar year.

There were 108 infants in the breech position at the time of delivery during this period; all but two of these (excluded from the study) were delivered by caesarean section. 50 were male and 56 were female. The mean duration of pregnancy at delivery was 37 weeks. An initial examination was performed in all cases within the first 48 hours postpartum, and treatment in a Pavlik harness commenced where there was clinical instability. Standardised AP and BIR views of the pelvis were taken at 4 months after birth, in all 106 cases. The acetabular index (AI) was measured on both sides.

There was only one case of hip dislocation at birth (bilateral dislocation in a first-born female infant). In 7 cases the initial examination was suspicious for instability, and patients were treated in Pavlik harness; in five of these cases another recognised risk factor (first-born female, family history) was also present. Two of these cases were found to have evidence of instability at 4 months, and underwent treatment by closed reduction and spica casting. For the entire group, the mean acetabular index (212 hips) was 23 degrees (range 17 to 36 degrees). Among those with signs suggestive of instability, the mean AI was 28 degrees. Only one patient had an AI > 30 degrees. Among those with no other risk factors, the mean AI was 22 degrees (range 17 to 28).

Our prospective study suggests that the incidence of DDH is markedly lower in breech presenters delivered by caesarean section (< 3%) that that reported for breech presenters as a whole. The three patients in our group with DDH had other risk factors present. We conclude that caesarean section may be protective for the development of DDH in infants who present in the breech position.