Management of extremely large birthweight infants presents challenges during the period of labour and delivery. We sought to examine outcomes in infants with extreme macrosomia (birthweight > 5000 g), at an institution where the management of labour is standardised.

Materials and Methods
This is a retrospective analysis of prospectively gathered data on all infants with a birthweight >5000 g delivered at a tertiary level institution from 2008 to 2012. Details of labour characteristics and outcomes were examined; these were compared according to parity.

During the study period, there were 46 128 deliveries at the hospital and 182 infants with a birthweight >5000 g, giving an incidence of 0.4%. The majority of women (133/182) were multiparous. Among nulliparas, 47% (23/49) had a vaginal delivery, while 53% (26/49) had a caesarean delivery. 86% (97/113) of multiparas had a vaginal delivery, and 14% (16/113) had a caesarean delivery. 43% (69/162) required induction of labour. This was more common in nulliparous compared with multiparous women (58% [29/49] vs 30% [40/133], P = 0.005, OR = 3.4, 95% CI = 1.7–6.6). A total of 30% (49/162) of women had their labour accelerated with oxytocin. There were higher rates of oxytocin use in nulliparas than in multiparas (55% [27/49] vs 16.5% [22/133], P < 0.0001, OR = 6.2, 95% CI = 3–12.8). Seventeen of the 120 infants delivered vaginally had a shoulder dystocia (14.2%), with three suffering an Erbs palsy, all of which had resolved before 6 months of age. One baby had a clavicular fracture. Conclusion Extreme macrosomia affects 0.4% of pregnancies in contemporary practice. Multiparas have a low rate of caesarean section. Infants delivered vaginally are at increased risk of shoulder dystocia and associated complications.