Preterm prelabour rupture of membranes before 23 weeks' gestation: prospective observational study.

Objective: To describe perinatal and maternal outcomes of preterm prelabour rupture of membranes (PPROM) before 23 weeks' gestation in a national cohort. Design: Prospective observational study. Setting: National population based cohort study with the UK Obstetric Surveillance System (UKOSS), a research infrastructure of all 194 obstetric units in the UK, 1 September 2019 to 28 February 2021. Participants: 326 women with singleton and 38 with multiple pregnancies with PPROM between 16+0 and 22+6 weeks+days' gestation. Main outcome measures: Perinatal outcomes of live birth, survival to discharge from hospital, and severe morbidity, defined as intraventricular haemorrhage grade 3 or 4, or requiring supplemental oxygen at 36 weeks' postmenstrual age, or both. Maternal outcomes were surgery for removal of the placenta, sepsis, admission to an intensive treatment unit, and death. Clinical data included rates of termination of pregnancy for medical reasons. Results: Perinatal outcomes were calculated with all terminations of pregnancy for medical reasons excluded, and a worst-best range was calculated assuming that all terminations for medical reasons and those with missing data would have died (minimum value) or all would be liveborn (maximum value). For singleton pregnancies, the live birth rate was 44% (98/223), range 30-62% (98/326-201/326), perinatal survival to discharge from hospital was 26% (54/207), range 17-53% (54/326-173/326), and 18% (38/207), range 12-48% (38/326-157/326) of babies survived without severe morbidity. The rate of maternal sepsis was 12% (39/326) in singleton and 29% (11/38) in multiple pregnancies (P=0.004). Surgery for removal of the placenta was needed in 20% (65/326) and 16% (6/38) of singleton and twin pregnancies, respectively. Five women became severely unwell with sepsis; two died and another three required care in the intensive treatment unit. Conclusions: In this study, 26% of women who had very early PPROM with expectant management had babies that survived to discharge from hospital. Morbidity and mortality rates were high for both mothers and neonates. Maternal sepsis is a considerable risk that needs more research. These data should be used in counselling families with PPROM before 23 weeks' gestation, and currently available guidelines should be updated accordingly.