The PHOENIX trial: when should labour be induced in women who develop pre-eclampsia at 34–37 weeks?

Professor Andrew Shennan, Professor Lucy Chappell, Ms Carolyn Gill, PHOENIX Consortium UK

The PHOENIX trial exists to find the best way of caring for women with pre-eclampsia during this “window” of pregnancy.

In women with pre-eclampsia, when the baby is delivered is of vital importance. Delivering the baby before the condition gets worse can avoid some of the effects of pre-eclampsia on mother and baby. However, it can also increase the risk of problems related to premature birth.

In women with mild pre-eclampsia near when the baby is due, inducing labour lowers the risk of problems to the mother without harming the baby. Pre-eclampsia which develops earlier in the pregnancy is often more serious. However, in between 34 – 37 weeks of pregnancy, it isn’t clear if a baby should be delivered or not. In the UK, about 10,000 women each year are seen for mild to moderate pre-eclampsia during this “window” – about a third of all women who get pre-eclampsia.

The PHOENIX trial exists to find the best course of action at this time during pregnancy. Women who experience pre-eclampsia at 34–37 weeks will be cared for in one of two ways. In half of the women, labour will be induced within 48 hours (or if necessary, the baby will be delivered by caesarean). The other half will be closely observed, and the baby will be only be delivered before 37 weeks if there are complications. This is called “expectant management,” or “wait and watch”.

As well as looking at the health of mother and baby, we will look at how babies were delivered, if the baby suffered from any breathing difficulties, and how parents felt about their care. When the babies are 2 years old, we will see how well they have developed by asking mothers to fill in a questionnaire about their child’s behaviour. We will also find out how much each way of treating women costs the NHS.

The first woman was enrolled into PHOENIX in September 2014. In total 47 centres and 731 women are now taking part, and we aim to recruit 900 women by the end of July 2018. We hope to find out if inducing early labour means fewer complications, fewer babies needing intensive care and fewer deaths, compared with the 'wait and watch' approach.

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This study takes place in a Tommy's centre and is funded by Tommy's and the National Institute for Health Research

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