Incidence and management of premature rupture of membranes in Victoria, Australia: A retrospective cohort study of 636 590 births between 2009 and 2017.

Background: Premature rupture of membranes (PROM) is a complication affecting 7-12% of pregnancies in which fetal chorioamniotic membranes rupture before labour begins. Preterm PROM (PPROM) (ie <37 weeks gestation) precedes one-third of preterm births, exposing the fetus to increased morbidity from placental abruption, respiratory distress syndrome and sepsis.

Aim: To analyse trends in the incidence and mode of birth in preterm and term PROM in Victoria, Australia between 2009 and 2017.

Materials And Methods: This retrospective population-based cohort study included all singleton pregnancies from 2009 to 2017. We examined women with PROM (both <37 weeks (PPROM) and at term). Management was assessed in three categories: (a) expectant management; (b) induction of labour (IOL); and (c) elective caesarean section (elCS). A multinomial logistic regression model was used to adjust for confounders influencing the choice of management.

Results: Of 636 590 singleton pregnancies, 52 669 (8.3%) births with PROM at term (42 439; 6.7%) or PPROM (10 230; 1.6%) were identified. Of these, the majority were managed expectantly (n = 22 726; 43.1%), or with IOL (25 931; 49.2%). While elCS represented only 7.6% of these cases (n = 4012), its use rose consistently from 2009 to 2017 for PROM at term and PPROM alike. For women with PPROM at 34-36 weeks the odds of elCS increased by 5% annually (adjusted odds ratio (aOR) 1.05; 95% CI 1.02-1.08) and 2% for IOL (aOR 1.02; 95% CI 1.00-1.05) vs expectant management.

Conclusions: The use of elCS and IOL in PPROM is rising in Victoria, particularly between 34 and 36 completed weeks of pregnancy. Research is needed to determine the drivers for this increase.