Antepartum Haemorrhage — Placenta Praevia, Placental Abruption, Vasa Praevia and Their Management

The RCOG defines antepartum haemorrhage (APH) as bleeding from or into the genital tract occurring from 24+0 weeks of pregnancy and before the birth of the baby. It complicates 3–5% of pregnancies and is a leading cause of perinatal and maternal death worldwide; up to one-fifth of very preterm babies are born in association with APH. The most important causes are placenta praevia and placental abruption, although they are not the most common ones.

1. Vital signs first — tachycardia or hypotension may reveal hypovolaemia from concealed bleeding (StatPearls)
2. Abdominal palpation — uterine tenderness, consistency, and the frequency and duration of contractions
3. Ultrasound to locate the placenta before any digital examination; a sterile speculum examination is safe (AFP)
4. Fetal assessment — continuous fetal heart monitoring when the gestation is viable; a category 3 tracing that does not resolve with resuscitation is an indication for delivery
5. Bloods — group and screen, CBC, fibrinogen, PT, aPTT and urea (StatPearls)
6. Rh-negative — Kleihauer–Betke test and anti-D immunoglobulin (AFP)
7. Supportive care — IV fluids, oxygen and monitoring while the history and examination are completed

Placenta praevia is the complete or partial covering of the cervix by the placenta. It affects 0.3–2% of pregnancies in the third trimester and is rising with caesarean rates (StatPearls). Nearly 90% of placentas called 'low-lying' on early scans resolve by the third trimester because the lower segment grows ('placental migration'), so an asymptomatic second-trimester finding is re-scanned later — AFP suggests around 28 weeks — before any delivery decision.

Risk factors (StatPearls): advanced maternal age (> 35), multiparity, smoking, cocaine use, prior suction curettage, assisted reproduction, previous caesarean section(s) and previous placenta praevia — the common thread is endometrial damage and uterine scarring. Placenta praevia on a scar raises the risk of placenta accreta spectrum (accreta, increta, percreta), in which villi invade beyond the Nitabuch fibrinoid layer.

• Stable, not bleeding: schedule elective caesarean at 36–37 weeks (StatPearls)
• Bleeding settles and < 36 weeks: expectant management is permissible
• Heavy or continuous bleeding: caesarean section regardless of gestational age
• Bleeding at 24–34 weeks: give antenatal corticosteroids (AFP)
• Rh-negative woman: give anti-D immunoglobulin after a Kleihauer–Betke test to size the dose (AFP)
• Suspected accreta spectrum: plan caesarean hysterectomy, leaving the placenta in situ to avoid torrential bleeding

After delivery, the lower uterine segment contracts poorly, so the placental bed keeps bleeding — praevia is a major risk factor for postpartum haemorrhage. Measures escalate from massage and uterotonics to balloon tamponade, B-Lynch and other compression sutures, uterine or internal iliac artery ligation or embolisation, and finally hysterectomy.

Placental abruption (abruptio placentae) is the premature separation of a normally implanted placenta from the uterine wall before delivery of the fetus. It occurs in about 0.4–1% of pregnancies, mostly before 37 weeks, and AFP calls it the most common cause of serious vaginal bleeding in late pregnancy.

• Hypertension and pre-eclampsia — see pre-eclampsia and eclampsia
• Smoking and cocaine use
• Age > 35, multiparity and previous abruption
• Abdominal trauma — road accident, fall, assault (ask tactfully about intimate partner violence)
• Sudden decompression of an overdistended uterus — rupture of membranes in polyhydramnios, or after delivery of the first twin (AFP)
• Short umbilical cord (AFP)

Classes 0–1 usually correspond to partial or marginal separation, and classes 2–3 to complete or central separation. Note that bleeding can be absent even in class 3 — the blood may be concealed behind the placenta.

In severe abruption, blood from the retroplacental haematoma infiltrates the myometrium and may reach the serosa, giving the uterus a purple, copper-coloured, ecchymotic appearance at caesarean section. This is the Couvelaire uterus (uteroplacental apoplexy). It is an operative finding, not a clinical diagnosis.

1. Resuscitate: IV access, fluids, oxygen, blood and blood products guided by serial haematocrit and coagulation studies
2. Continuous maternal and fetal monitoring where the gestation is viable
3. Class 1, stable, < 37 weeks: conservative inpatient care with serial growth scans; tocolysis is generally contraindicated except in mild abruption before 34 weeks to allow steroids (AFP)
4. Class 2–3 with a live viable fetus: deliver — caesarean if fetal distress or maternal decompensation
5. Fetal death: immediate delivery; vaginal birth often carries less maternal risk when coagulopathy is present, and hypertonic contractions make labour rapid
6. After delivery: watch for PPH and worsening coagulopathy

Vasa praevia exists when exposed fetal vessels run through the membranes between the presenting part and the internal cervical os, unprotected by placental tissue. When the membranes rupture — spontaneously or at amniotomy — these vessels tear and the fetus exsanguinates rapidly; the bleeding is fetal blood, so the mother is stable while the fetal heart deteriorates. The incidence is about 1 in 2,500 births (AFP).

• Risk factors: low-lying placenta in the second trimester, velamentous insertion, bilobed/succenturiate placenta, IVF and multiple pregnancy
• Diagnosis: transvaginal colour Doppler showing vessels over the os; in labour, painless bleeding at membrane rupture with fetal heart decelerations
• Apt test: detects fetal haemoglobin by its resistance to alkali denaturation — but never delay delivery for it when bleeding is severe or the fetal heart is abnormal (AFP)
• Management: planned caesarean before membranes rupture, typically around 34–35 weeks after corticosteroids (Donnolley); no amniotomy