Obstetric and neonatal risks among extremely macrosomic babies and their mothers.

OBJECTIVE: We estimated the risk of complications at birth of extremely large babies (>= 5000 g). STUDY DESIGN: This was a cohort study including all births of extremely large babies in 1996 through 2005 and comparison cohort with normal birthweight (1:2) identified in the national birth registration. RESULTS: There were 343 extremely large babies or 0.9% of all singletons. Compared to the normal birthweight cohort (n = 679), there were increased odds of shoulder dystocia (odds ratio [OR], 26.9; 95% confidence interval [CI], 11.1-65.1), emergency cesarean section (OR, 5.2; 95% CI, 3.4-8.0), and failed labor induction (OR, 4.3; 95% CI, 1.7-11.0). The risk of elective section was not increased (OR, 1.1; 95% CI, 0.6-2.0). Minor congenital malformations were more frequent (OR, 2.1; 95% CI, 1.2-3.7), as were birth injuries (OR, 3.7; 95% CI, 2.16.8) and minor metabolic disturbance (OR, 2.5; 95% CI, 1.1-6.2), but not asphyxial births. CONCLUSION: The risk of shoulder dystocia for very large babies is markedly raised, as are minor complications, while for mothers the main risk is emergency section.