Preterm birth risk: cervix, history, symptoms, and prevention

Preterm birth is birth before 37 completed weeks. Specialist assessment is most useful when it distinguishes three related but different situations: a woman with a previous spontaneous early birth, a shortened cervix found on ultrasound, and symptoms that may represent current preterm labour.

Previous preterm birth

The details of a previous birth matter. Spontaneous labour, preterm rupture of membranes, medically indicated delivery for pre-eclampsia, and birth after fetal or placental compromise do not carry identical recurrence pathways. Reviewing gestation, cervical procedures, uterine anatomy, infection history, placental findings, and the reason for delivery helps select surveillance and prevention.

Cervical-length assessment

Transvaginal ultrasound is the standard way to measure cervical length when indicated. A short cervix does not always lead to early birth, but it can identify a group in whom progesterone or cerclage may be considered depending on gestation, obstetric history, symptoms, dilation, and whether the pregnancy is singleton or multiple. A treatment decision should not be based on an unconfirmed abdominal measurement alone.

Symptoms need triage

Regular painful contractions, pelvic pressure, persistent lower back pain, vaginal bleeding, or fluid leakage before 37 weeks needs prompt maternity assessment. Many symptomatic women will not deliver immediately; examination and appropriate testing help avoid both false reassurance and unnecessary treatment.

When hospital treatment is considered

If preterm birth appears likely, management may include antenatal corticosteroids to support fetal lung maturation, magnesium sulfate for fetal neuroprotection at very preterm gestations, short-term medication to delay labour in selected situations, antibiotics when membranes rupture or infection is suspected, and transfer to a hospital with the neonatal capability appropriate for gestational age.

The central question is time: whether the pregnancy can safely continue, whether a short delay creates meaningful benefit, and where mother and baby should be cared for if birth cannot be prevented.