Maternal prepregnancy obesity and the risk of shoulder dystocia: a meta-analysis

Background: Results from epidemiological studies about the association between maternal prepregnancy obesity and the risk of shoulder dystocia are inconsistent.

Objective: To evaluate the effect of maternal prepregnancy obesity on the risk of shoulder dystocia.

Search strategy: We searched PubMed and the Web of Science database for all relevant studies up to 5 August 2016 and reviewed the reference lists of identified articles.

Selection criteria: Observational studies that investigated the association between prepregnancy obesity and the risk of shoulder dystocia were included.

Data collection and analysis: A total of 20 articles involving 2 153 898 participants were included in this meta-analysis. A random-effects model was used to calculate the pooled relative risks (RRs) with 95% CIs.

Main results: For obese versus nonobese, the pooled RR of shoulder dystocia was 1.63 (95% CI: 1.33-1.99). The findings remained significant in the cohort studies (RR = 1.57, 95% CI: 1.28-1.93) and case-control studies (RR = 2.70, 95% CI: 1.46-4.98). With regard to the subgroup 'continents', there was a significant association between obesity and the risk of shoulder dystocia in Europe (RR = 1.51, 95% CI: 1.18-1.92) and Asia (RR = 2.59, 95% CI: 1.15-5.83). The result from the sensitivity analysis for studies adjusted for gestational diabetes was significant (RR = 1.61, 95% CI: 1.05-2.47). The pooled RRs for obesity classes I, II and III versus nonobese were 1.29 (95% CI: 1.06-1.57), 1.94 (95% CI: 1.26-2.98) and 2.47 (95% CI: 1.56-3.93), respectively.

Conclusion: This meta-analysis suggests that maternal prepregnancy obesity is associated with an increased risk of shoulder dystocia.

Tweetable abstract: A meta-analysis shows that maternal prepregnancy obesity increases the risk of shoulder dystocia.