Use of birth weight threshold for macrosomia to identify fetuses at risk of shoulder dystocia among Chinese populations

Objective To assess the incidence of macrosomia and the influence of birth weight on shoulder dystocia risk among a cohort of Chinese women. Methods A retrospective analysis was conducted of 80 953 singleton deliveries recorded at the Prince of Wales Hospital, Hong Kong, between 1995 and 2009. The incidences of macrosomia (birth weight ≥ 4000 g) and shoulder dystocia were assessed by birth weight; risk factors for shoulder dystocia were examined by multiple logistic regression analysis. Results The incidence of macrosomia was 3.4%. The overall incidence of shoulder dystocia was 0.3%; however, the incidence rose with increasing birth weight. The odds ratio (OR) for a birth weight of 4000–4199 g was 22.40, while the OR for a birth weight of 4200 g or above was 76.10. Other independent risk factors for shoulder dystocia included instrumental delivery (OR 12.11), short stature (OR 2.16), maternal diabetes mellitus (OR 1.78), and obesity (OR 1.58). Conclusion Although the overall incidences of macrosomia and shoulder dystocia were low, the risk of shoulder dystocia was strongly linked to increasing birth weight. International guidelines for elective cesarean delivery in suspected cases of macrosomia may not, therefore, apply to Chinese women.