Why does preterm labour cause waters breaking?

The baby is surrounded by fluid held inside thin membranes. During preterm labour, pressure from uterine contractions can strain these membranes. Changes in the tissues, including inflammation, may make them less able to hold the fluid, causing a gush or a slow, persistent leak from the vagina.

The fluid may be clear, pale or slightly blood-stained, and it can be difficult to distinguish from urine or increased discharge. Once the membranes may have ruptured, the maternity team needs to check the fluid, your health and the baby’s wellbeing.

Call your maternity unit immediately if you think your waters have broken before labour, particularly before your due date. Use a clean maternity pad, note the colour and smell of the fluid, and avoid putting anything into the vagina until you have received advice.

Tell the team about contractions, bleeding, pain, fever or changes in fetal movement. Do not rely on a home test or wait for a larger gush; a slow leak also deserves assessment.

Seek emergency maternity care for heavy bleeding, green or foul-smelling fluid, fever, severe abdominal pain, feeling very unwell, reduced fetal movement or an urge to push. These signs can require rapid assessment and treatment.

Ask: Have my membranes ruptured? How will you check for infection? How will my baby be monitored? Should I expect contractions? Which changes in fluid or movement require urgent return?