The WILL Trial – an update

The WILL trial aims to investigate the clinical effectiveness and cost-consequences of planned early term delivery at 38+0 to 38+3 weeks’ gestation, compared with expectant care at term until at least 40+0 weeks’ gestation, in pregnant women with chronic or gestational hypertension that develops by 37+6 weeks’ gestation. 

High Blood pressure in pregnancy?  When is the best time to deliver?

The WILL trial is investigating when is the best time to deliver at term, for women with high blood pressure in pregnancy but without pre-eclampsia: 38+0 to 38+3 weeks or at least 40+0 weeks of pregnancy.

Currently, there is no good information on which to base this timing of delivery decision, so there is variation in clinical practice.

Eligible women who provide consent to take part in WILL are randomly assigned to planned delivery at 38+0-3 weeks or planned expectant care until at least 40+0 weeks. Data will be collected about the outcome of pregnancy, birth and initial postnatal period to assess if there are better outcomes for women and their babies in one of the timing of delivery groups than the other.

The WILL trial is currently recruiting in 24 consultant-led maternity units in the UK, and more participating sites are opening. Eligible women will be invited to join the trial until the end of 2022, with an aim to have more than 1,000 pregnant women involved, to help us answer this important research question. To date, 131 women have agreed to participate.

If you would like more information or would like to get involved, please contact the WILL trial team at Birmingham Clinical Trials Unit by email ( or telephone (0121 4159109) or visit the trial website (

Have you had high blood pressure (hypertension) in pregnancy? Would you be interested in joining a Public Patient Involvement (PPI) Working Group for WILL?

The aim of this group is to help us by: reviewing the trial materials and trial progress to date, assisting us in problem-solving about barriers to recruitment, and reviewing trial progress and plans for how to share information with women when the trial has been completed.

We are looking for more people to be involved, so please do get in touch by email (, follow our twitter page ( or telephone (0121 4159109).