Population:
The study population was all births occurring at or beyond 24 weeks’ gestational age in a major inner-city hospital network in Sydney, Australia, and has been described in a previous publication.9 Group A consisted of births from August 1989 to December 1999, when the annual caesarean delivery rate ranged from 18% to 20%. Group B consisted of births from January 2009 to December 2016, when the annual caesarean delivery rate ranged from 30% to 32%.