Maternal and neonatal complications of fetal macrosomia: cohort study

Objective: To estimate risks of maternal and neonatal complications in pregnancies with macrosomia.

Method: This was a retrospective cohort study undertaken at a large maternity unit in United Kingdom between January 2009-December 2016. We compared the incidence of complications in pregnancies with macrosomia, defined by birthweight (BW)>4,000 g and severe macrosomia with BW>4,500 g, to those in pregnancies with normal BW 2,500-4,000 g. Regression analysis was undertaken to determine odds ratios (OR) [95% confidence interval (CI)] for pregnancy complications in macrosomic compared to normal BW group.

Results: The study population of 35,548 pregnancies included 4,522 (12.7%) with macrosomia, 643 (1.8%) with severe macrosomia and 31,026 (87.3%) with normal BW. In macrosomia group, adjusted OR was 3.07 (95%CI:1.64,2.01) for cesarean section for failure to progress, 2.40 (95%CI:1.95,2.96) for post-partum haemorrhage, 2.29 (95%CI:1.86,2.82) for sphincter injury, 10.37 (95%CI:8.57,12.55) for shoulder dystocia, 28.48 (95%CI:8.94,90.67) for brachial plexus injury, 32.33 (95%CI:3.76,278.15) for birth fractures and 4.40 (95%CI:2.20,8.82) for hypoxic-ischemic encephalopathy. The respective values for severe macrosomia were 4.32 (95%CI:3.05,6.13), 2.93 (95%CI:1.93,4.44), 3.12 (95%CI:1.92,5.08), 28.74 (95%CI:20.75,39.79), 73.92 (95%CI:15.05,363.16), 87.17 (95%CI:7.72,984.96) and 13.77 (95%CI: 5.16,36.75).

Conclusion: Macrosomia is associated with serious adverse perinatal outcomes. This study provides accurate estimates of risks to aid in pregnancy management.