Association between timing and duration of breech presentation during pregnancy and developmental dysplasia of the hip: A case-control study.

This case-control study investigated the association between timing and duration of breech presentation in pregnancy and developmental dysplasia of the hip (DDH). Children with DDH aged 3 years or younger (n = 191) were compared with healthy controls (n = 209). Data on outcome, exposure and, covariates were collected using a parents' self-report online questionnaire. Term children with breech presentation at one or more check-ups after 30.0 weeks gestation had a twofold higher risk of developing DDH compared to children who had never presented in breech (OR 2.01; 95% CI [1.28, 3.15]). The strength of the association increased with duration of breech presentation (5-8 weeks: OR 2.65; 95% CI [1.36, 5.18]; 9-12 weeks: OR 3.63; 95% CI [1.82, 7.24]). Children who had presented in breech at least once in gestational period 37.0-birth had a 3.24 (95% CI [1.86, 5.65]) times higher risk of DDH, whereas the risk for children with breech presentation in gestational period 30.0-36.6 only was not increased. Also after adjusting for confounders, children who had presented in breech after gestational week 37.0-birth had a more than threefold higher risk of DDH (OR 3.33; 95% CI [1.81, 6.13]) compared to children who were never in breech or in gestational period 30.0-36.6 only.