Risk factors of developmental dysplasia of the hip in infants: A meta-analysis based on cohort studies

Introduction: Developmental dysplasia of the hip (DDH) is a prevalent condition in children. Currently, the exact etiology of DDH remains uncertain. The objective of this study was to conduct a meta-analysis to investigate the risk factors associated with DDH in infants. The findings would provide a theoretical foundation for targeted early screening and diagnosis. Hypothesis: Several indicators, such as gender, intrauterine position, family history of DDH, gestational age, delivery mode, amniotic fluid levels, swaddling, parity, fetus number, combined musculoskeletal deformities, birth weight, and physical examination results, may serve as risk factors for DDH. Materials and methods: Cohort studies investigating the risk factors of DDH in infants through logistic regression analysis were searched in the Wanfang, VIP citation, China National Knowledge Infrastructure (CNKI), China Biology Medicine disc, Excerpta Medica Database (Embase), PubMed, and Cochrane Library databases up to May 2023. After extracting the data from eligible literature and assessing them using the Newcastle-Ottawa Scale (NOS), articles were selected based on pre-established inclusion and exclusion criteria. Results: A total of eleven literature reports covering 979,757 infants were included in this meta-analysis. The publication bias did not significantly influence the results. The incidence rate of DDH was 47.99‰ among infants with risk factors compared to 3.21‰ in the general population. Risk factors for DDH included being female (OR = 6.97, 95% CI: 5.18-9.39, p < 0.001), breech delivery (OR = 4.14, 95% CI: 3.09-5.54, p < 0.001), positive family history (OR = 4.07, 95% CI: 2.20-7.52, p < 0.001), cesarean section (OR = 1.11, 95% CI: 1.01-1.21, p = 0.032), oligohydramnios (OR = 3.93, 95% CI: 1.29-12.01, p = 0.016), swaddling (OR = 6.74, 95% CI: 1.25-36.31, p = 0.026), firstborn status (OR = 1.84, 95% CI: 1.49-2.53, p < 0.001), combined musculoskeletal malformations (OR = 2.27, 95% CI: 1.58-3.27, p < 0.001), and physical signs of DDH (OR = 8.71, 95% CI: 2.44-31.07, p = 0.001). Premature delivery (OR = 0.91, 95% CI: 0.88-0.95, p < 0.001) was a protective factor for DDH. The relationship between multiple pregnancies (OR = 0.58, 95% CI: 0.33-1.02, p = 0.060) and low birth weight (OR = 0.62, 95% CI: 0.14-2.76, p = 0.529) in relation to DDH remained uncertain. Discussion: This meta-analysis shows that female, breech delivery, positive family history, cesarean section, firstborn status, oligohydramnios, swaddling and combined musculoskeletal malformations are associated with DDH. Premature delivery appeared to be a protective factor against DDH. Nevertheless, the other factors need more research to reach more conclusive results. Level of evidence: III; Meta-analysis.