When is birth optimal for women with chronic or gestational hypertension at term?.

Planned early term birth may reduce maternal morbidity and pre-eclampsia.

Ongoing expectant care may reduce neonatal morbidity.

The WILL trial is designed to resolve these uncertainties.

To address optimal timing of birth for women with chronic or gestational hypertension who reach term and remain well.

Pragmatic, non-masked randomised trial. Inclusion: maternal age ≥16 years, chronic or gestational hypertension, singleton pregnancy, live fetus, 36+0–37+6 weeks’ gestation, and able to give documented informed consent. Exclusion: contraindication to either trial arm (e.g., pre-eclampsia or another indication for birth at term), blood pressure (BP) ≥ 160/110 mmHg until controlled, major fetal anomaly anticipated to require neonatal care unit admission, or participation in another timing of birth trial. Randomisation (1:1 ratio, minimised for key prognostic variables: site, hypertension type, and prior Caesarean) to ‘planned early term birth at 38+0-3 weeks’ or ‘usual care at term’ (revised from ‘expectant care until at least 40+0 weeks’, Aug 2022).

Maternal co-primary: composite of ‘poor maternal outcome’ (severe hypertension, maternal death, or maternal morbidity). Neonatal co-primary: neonatal care unit admission for ≥4 h. Each co-primary is measured until primary hospital discharge or 28 days post-birth (whichever is earlier). Key secondary: Caesarean birth.

Sample of 1080 participants (540/arm) will detect an 8% reduction in the maternal co-primary (90% power, superiority hypothesis), and give 94% power for a between-group non-inferiority margin of difference of 9% in the neonatal co-primary. Analysis will be by intention-to-treat. Ethics approval has been obtained (NHS Health Research Authority London Fulham Research Ethics Committee, 18/LO/2033).

The study will provide data for women to make informed choices about their care and allow health systems to plan services.

Pregnancy

Hypertension

Timing of birth

Induction

Maternal outcomes

Perinatal outcomes

© 2023 The Authors. Published by Elsevier B.V. on behalf of International Society for the Study of Hypertension in Pregnancy.