What causes preterm labour?

Labour may start early after the membranes break, with infection or inflammation, or when bleeding irritates the uterus. A uterus stretched by more than one baby or excess amniotic fluid may contract sooner. A cervix that shortens or opens without strong contractions can also contribute.

Previous spontaneous preterm birth, some uterine or cervical differences, smoking, and certain maternal health or placental problems can increase vulnerability. Sometimes clinicians recommend early delivery because continuing the pregnancy poses a greater risk to the pregnant person or baby; this is different from spontaneous preterm labour. Having a risk factor does not mean labour will start early.

Call your maternity unit without waiting for a routine visit if you have regular tightenings, period-like cramps, new lower backache, pelvic pressure, a change in vaginal discharge, fluid leaking from the vagina, or vaginal bleeding before full term. Note when symptoms began and whether the baby is moving in its usual pattern.

The maternity team may monitor contractions and the baby's heartbeat, examine the cervix, check for fluid leakage or infection, and use ultrasound or other tests when suitable. Depending on gestation and findings, care may include observation, transfer to an appropriate maternity unit, medicine to delay birth briefly, or antenatal steroid injections to support the baby's preparation for birth.

Seek urgent maternity assessment for a gush or ongoing trickle of fluid, vaginal bleeding, strong or increasingly frequent contractions, severe abdominal pain, fever or chills, or reduced or changed fetal movement. Use emergency services if there is heavy bleeding, collapse, severe pain, or an urge to push and birth appears imminent.

Ask what the examination shows about the cervix and membranes, whether infection testing is needed, and what monitoring is planned. If you have had an earlier preterm birth or cervical procedure, discuss whether cervical-length surveillance, progesterone, or cervical cerclage is relevant to your circumstances.