Preterm birth subtypes
The primary study outcome was PTB < 37 completed weeks’ gestation. PTB was further categorized as spontaneous PTB or provider-initiated PTB.1 Births that result from spontaneous preterm labour and PPROM were classified as spontaneous PTB, while preterm birth that resulted from labour induction or caesarean delivery for maternal or fetal indications were classified as provider-initiated PTB. As a secondary outcome, we assessed the outcome of early PTB < 34 weeks’ gestation.