AKT · Obstetrics & gynaecology/Late pregnancy & labour

Placenta praevia

Placenta over/near the internal cervical os

Overview

Placenta lying wholly or partly over the lower uterine segment/internal os. Classically causes PAINLESS antepartum bleeding; diagnosed on USS and managed to avoid digital examination and to plan caesarean delivery.

Recognise

PAINLESS bright-red vaginal bleeding (often recurrent) after 24 weeks
Soft, non-tender uterus; high presenting part/malpresentation
Often found on the anomaly scan before any bleeding

Red flags

Major haemorrhage; placenta accreta spectrum (esp. with prior caesarean)

Differentials & how to tell them apart

Placental abruptionPAINFUL, tense tender uterus, fetal distress

Vasa praeviableeding at ROM with fetal compromise

Local cervical causeminor, after praevia excluded

Investigations

Transvaginal USS (safe and accurate) locates the placenta. NO digital vaginal examination. Screen for accreta if anterior praevia + prior caesarean (MRI).

Management

Planned caesarean section; manage bleeds with resuscitation + steroids

1Confirmed praevia: avoid intercourse/vaginal exams; corticosteroids if preterm risk; plan elective caesarean (~36–37 weeks).Gate: Any praevia → deliver by CAESAREAN (vaginal delivery is contraindicated)
2Acute bleed: resuscitate, anti-D if rhesus-negative, expedite delivery if severe; manage accreta spectrum with specialist MDT.

Corticosteroids — fetal lung maturation if preterm delivery likely

Anti-D — rhesus-negative

Blood/resuscitation — for haemorrhage

Key points

A low-lying placenta on the 20-week scan often migrates upward — rescan at ~32 weeks before labelling praevia. Prior caesarean + anterior praevia raises accreta risk.

Monitor & prognosis

Placental position (rescan), bleeding, fetal growth.

Good with planned caesarean; accreta is the danger.

Source: RCOG Green-top 27a