The Big Baby Trial    The Perinatal Institute, in collaboration with Warwick University, CTU and Coventry & Warwickshire NHS Trust, has been awarded an NIHR grant to conduct a national randomised controlled trial to investigate the management of antenatally suspected macrosomia (babies with an ultrasound scan estimated fetal weight over 90th customised centile). The protocol will aim to establish whether induction of labour at 38 weeks will reduce the incidence of shoulder dystocia and other complications for mother and baby. The trial will start in 2018 and will involve 60 GAP Trusts and Health Boards across the UK.

Key Information

Title: Induction of labour for predicted macrosomia - The 'Big Baby' Trial

Chief Investigators:
Professor Siobhan Quenby - University of Warwick
Professor Jason Gardosi - Perinatal Institute

Sponsor: University Hospitals Coventry and Warwickshire NHS Trust

Funder: This project was funded by the National Institute for Health Research Health Technology Assessment Programme (project number 16/77/02)

Difficulty in delivering the shoulders, after a baby’s head has been delivered, can be a serious complication during a vaginal birth. In most cases where this happens, the baby is larger than average. It has been suggested that if we can predict, by ultrasound scan in the last weeks of pregnancy, which babies are particularly large and at the highest risk of shoulder dystocia, then we could deliver them a week or two earlier by inducing labour, which would reduce the chance of this complication.

It is not clear whether it is better for women and their babies to have labour induced early or to wait for labour to begin naturally. To find out whether delivering large babies earlier is the right thing to do for the baby and mother, a clinical trial is needed. We propose to study 4,000 pregnant women whose ultrasound scans suggests that their babies are particularly large and may be at risk of difficulty with delivery of the shoulders during birth.

With the woman’s consent, she will be allocated at random into either an early induction of labour group, with the aim to give birth at, or soon after, 38 weeks, or a control group where care is as usual and the start of labour is awaited, unless it becomes necessary to induce labour after 38 weeks. We will compare outcomes between the two groups to look at whether, as a result of induction of labour at about 38 weeks, there were fewer complications such as difficulty with the delivery of the baby’s shoulders. We will also assess the benefits and risks to women and their babies in each group.

This trial will help decide what the safest method is to care for pregnant women where, because of the large size of the baby, complications may occur during labour and birth.

Sample size: 4000 women identified as having large for gestational age pregnancies.

Primary outcome: The incidence of shoulder dystocia (with assessment of the validity of the diagnosis, for all randomised women, by an independent expert group)

Duration: 42 months: 01/01/2018 - 30/06/2021.

Further details to follow. Please also see University of Warwick website: