Timing of birth to improve outcomes in chronic or gestational hypertension: the WILL RCT.

Background: For women with chronic or gestational hypertension who remain well, early term birth (at 37-38 weeks' gestation) may reduce maternal complications, caesareans and stillbirths, but it may increase neonatal morbidity compared with expectant care. Expectant care may increase costs. There are no high-quality data to guide care, which currently involves maternal-fetal surveillance and intervention for maternal or fetal compromise, which may be rapid or unexpected. Objective: To investigate optimal timing of birth for women with chronic or gestational hypertension who reach term and remain well. Design: Pragmatic, unmasked, multicentre randomised trial with a health economic analysis. Setting: Fifty United Kingdom hospitals. Participants: Inclusion: maternal age ≥ 16 years, chronic or gestational hypertension, singleton pregnancy, live fetus, 36 Interventions: Planned early term birth at 38 Main outcome measures: Maternal coprimary: composite of 'poor maternal outcome' (severe hypertension, maternal death or maternal morbidity and superiority hypothesis). Neonatal coprimary: neonatal care unit admission ≥ 4 hours (non-inferiority hypothesis). Each coprimary is measured until primary hospital discharge or 28 days post birth (whichever is earlier). Key secondary: caesarean birth. Randomisation: 1 : 1 ratio, minimised for key prognostic variables: site, hypertension type and prior caesarean. Blinding: It was not possible to mask care providers or participants to the intervention. For the coprimary maternal outcome, there was local site principal investigator/delegate sign-off based on review, masked to allocated group, of primary case notes. Results: From 2019 to 2022, 403 participants were randomised (37% of target 1080) to intervention ( Limitations: Recruitment was 37% of the anticipated sample size (as above). Conclusions: Despite being unable to recruit to target in this study, we observed that most women with chronic or gestational hypertension required labour induction and planned birth at 38 Future work: An individual participant data meta-analysis is planned to address whether the intervention (vs. control) reduces caesarean; low adverse event rates would make unfeasible mounting another randomised trial. Funding: This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme as award number 16/167/123.