Obstetrics and Gynaecology chapters
Antepartum haemorrhage: placenta praevia, placental abruption and vasa praevia
Bleeding from the genital tract in the second half of pregnancy: how to tell placenta praevia from placental abruption and vasa praevia, what not to do on examination, and how each is managed.
- Antepartum haemorrhage is bleeding from the genital tract from 24 weeks (some texts say 20) until delivery. The big three are placenta praevia, placental abruption and vasa praevia.
- Praevia: painless, bright red, recurrent bleeding, soft uterus, high head or malpresentation; no digital vaginal examination until a scan has located the placenta. Abruption: painful bleeding with a tense, tender uterus and fetal distress; blood loss may be concealed.
- Resuscitate first, then cross-match, Kleihauer and anti-D if rhesus negative, steroids if preterm, and deliver when mother or baby is at risk; vasa praevia needs immediate caesarean section.
On this page
Overview
Antepartum haemorrhage (APH) is bleeding from the genital tract after 24 weeks of pregnancy and before the birth of the baby. Ten Teachers uses 24 weeks in one chapter and 20 weeks in another, and some Pakistani texts still use 28 weeks; check the definition your exam expects. Bleeding before this point is managed as threatened miscarriage.
- APH affects about 3% of pregnancies: roughly 1% placenta praevia, 1% placental abruption and 1% other causes.
- Placental bleeding can kill both mother and baby. Bleeding in pregnancy and after birth remains one of the main reasons mothers die worldwide, including in Pakistan.
Causes
| Group | Causes |
|---|---|
| Placental | Placental abruption, placenta praevia |
| Fetal | Vasa praevia |
| Local (maternal) | Cervical ectropion, cervicitis, vaginal infection, vaginal trauma, cervical cancer, polyps |
| Unexplained | No cause found in many minor bleeds |
Initial assessment of any APH
History
- How much blood? Fresh or dark?
- Was there a trigger (e.g. bleeding after intercourse)?
- Pain or contractions?
- Is the baby moving?
- Date and result of the last cervical smear.
Examination
- Pulse and blood pressure, signs of shock.
- Uterus: soft and non-tender, or hard and tender?
- Lie and presentation; fetal heart by auscultation or CTG.
- Speculum examination to see the cervix, but only after the placenta is known not to be praevia (ideally with a bedside scan).
Investigations
- FBC, clotting screen, group and cross-match (Ten Teachers suggests 6 units if praevia or abruption is suspected).
- Kleihauer test and anti-D if rhesus negative.
- Ultrasound: placental site, fetal size and presentation, liquor.
No digital vaginal examination until placenta praevia has been excluded. A finger through the cervix can provoke torrential bleeding.
Placental abruption
Definition
Premature separation of a normally sited placenta from the uterine wall before the birth of the baby. Blood collects between the placenta and the uterus.
Risk factors
- Hypertension and pre-eclampsia (the commonest association).
- Previous abruption.
- Smoking and cocaine.
- Abdominal trauma (road accidents, falls, domestic violence).
- Multiple pregnancy and polyhydramnios (sudden decompression when membranes rupture).
- FGR, thrombophilia, older mothers, preterm prelabour rupture of membranes.
Types
| Type | Description |
|---|---|
| Revealed | Blood tracks down behind the membranes and out through the cervix |
| Concealed | Blood stays trapped behind the placenta; little or no visible bleeding despite major loss |
| Mixed | Both |
Clinical features
- Painful vaginal bleeding, often dark blood.
- Tense, rigid, tender ("woody") uterus; may be larger than dates.
- Shock out of proportion to the visible bleeding (concealed loss).
- Fetal parts hard to feel; fetal heart hard to hear, reduced movements, abnormal CTG or fetal death.
- Possible labour.
The amount of visible bleeding does not show the size of an abruption. A large concealed abruption may show almost no blood at the vulva.
A normal ultrasound does not exclude abruption. Diagnosis is clinical.
Complications
- Maternal: hypovolaemic shock, disseminated intravascular coagulation (DIC), acute kidney injury, postpartum haemorrhage, blood into the myometrium (Couvelaire uterus), death.
- Fetal: hypoxia, prematurity, FGR, stillbirth. Separation of half the placenta or more is often fatal to the fetus.
Management
- Call senior help; resuscitate: two large-bore cannulas, bloods, cross-match, fluids and blood, urine output.
- Correct coagulopathy.
- Fetus alive and distressed, or mother unstable: deliver urgently, usually by caesarean section.
- Fetus dead: aim for vaginal delivery once the mother is stable (amniotomy and oxytocin), with aggressive correction of clotting.
- Small abruption, stable mother, healthy preterm fetus: admit, monitor, give steroids if preterm, anti-D if rhesus negative.
- Anticipate PPH after delivery.
Placenta praevia
Definition
A placenta that is implanted wholly or partly in the lower uterine segment, over or near the internal os. Bleeding comes from the maternal circulation as the lower segment stretches and the placenta shears off.
Risk factors
- Previous caesarean section (risk rises with each one).
- Multiple pregnancy (large placenta).
- Uterine structural anomaly.
- Assisted conception.
- High parity and older age.
Clinical features
- Painless, bright red, often recurrent bleeding, sometimes after intercourse, sometimes with no trigger.
- The first bleed is often small (a "warning" bleed).
- Soft, non-tender uterus.
- Malpresentation (breech, transverse or oblique lie) or a high, unengaged head, because the placenta occupies the pelvis.
- Fetal heart usually normal; the mother is at more risk than the baby.
- Bleeding may trigger contractions, so some pain does not rule praevia out.
Diagnosis
- Ultrasound, preferably transvaginal, which safely measures the distance from the placental edge to the internal os.
- A low-lying placenta is seen in about 15-20% of women at the 20-week anomaly scan, but as the lower segment forms most of them "migrate" upwards; only about 10% remain praevia. Such women are rescanned in the third trimester.
"Praevia is Painless, abruption Aches."
Management
- Resuscitate if bleeding is heavy; deliver irrespective of gestation if mother or fetus is in danger (still try to give steroids).
- If bleeding settles: admit for at least 48 hours, because re-bleeding is common in this window.
- Steroids if there is significant bleeding (over 500 ml) and the gestation is under 35 weeks.
- Kleihauer and anti-D if rhesus negative.
- Keep blood available; correct anaemia.
- Delivery by caesarean section by a senior obstetrician when the placenta covers or lies close to the os.
Placenta accreta spectrum
- The placenta grows into (accreta), deep into (increta) or through (percreta) the myometrium, with little or no decidua between.
- The main risk is a praevia over a previous caesarean scar; the chance climbs steeply with each caesarean.
- It causes massive haemorrhage at delivery; plan with consent for transfusion, interventional radiology, leaving the placenta in place or hysterectomy.
A woman with placenta praevia and a previous caesarean must be assessed for placenta accreta.
Vasa praevia
- Fetal vessels run through the membranes over the internal os, unprotected by placenta or cord.
- Causes: velamentous cord insertion or vessels joining a succenturiate (accessory) lobe.
- Classic picture: painless fresh bleeding at rupture of membranes (spontaneous or artificial), followed quickly by fetal bradycardia or death.
- The blood lost is fetal, so the mother is not at risk but the baby can exsanguinate.
- Management: emergency caesarean section if the baby is alive.
Comparison
| Feature | Placenta praevia | Placental abruption | Vasa praevia |
|---|---|---|---|
| Pain | Painless | Painful | Painless |
| Bleeding | Bright red, recurrent, matches shock | Dark; may be concealed; shock out of proportion | Fresh, at membrane rupture |
| Uterus | Soft, non-tender | Tense, tender, woody | Soft |
| Presenting part | High or malpresentation | Usually normal | Usually normal |
| Fetal heart | Usually normal | Often distressed or absent | Bradycardia, rapid death |
| Main danger | Mother | Fetus (and mother: DIC) | Fetus |
| Key test | Ultrasound (TVS) | Clinical diagnosis | Clinical; scan may show vessels |
Local causes
If the bleeding is minor, the placenta is normally sited and the cervix is seen clearly, local causes are treated directly (e.g. antifungal for candida), provided cervical cancer has been excluded by smear history and inspection.
Expect: the definition and incidence of APH; painless bright red recurrent bleeding with a soft uterus and malpresentation in praevia versus painful bleeding with a tense tender uterus and fetal distress in abruption; concealed abruption and shock out of proportion; hypertension, smoking, trauma and polyhydramnios as abruption risks; previous caesarean as a praevia and accreta risk; no digital examination before a scan; transvaginal scan for diagnosis; migration of low-lying placentas; admission for 48 hours; DIC and PPH after abruption; vasa praevia with fetal bleeding at membrane rupture and emergency caesarean.
Quick revision
- APH: bleeding from 24 weeks (some say 20) to delivery; about 3% of pregnancies.
- Praevia: painless, recurrent, bright red; soft uterus; high head; ultrasound diagnosis.
- No vaginal examination until the placenta is located.
- Abruption: painful, tense woody uterus, fetal distress; may be concealed; DIC.
- Abruption risks: hypertension, smoking, cocaine, trauma, polyhydramnios, twins.
- Praevia risks: previous caesarean, twins, uterine anomaly, IVF.
- Praevia with a scar: think accreta.
- Vasa praevia: fetal blood, bleeding at membrane rupture, emergency caesarean.
Written by The House Job from standard references (Obstetrics by Ten Teachers).
FAQ
Why is abruption painful but praevia painless?
In abruption blood is forced into and behind the placental bed, irritating and distending the muscle; in praevia the placenta simply separates from the stretching lower segment.
Why can a woman with abruption be shocked with little visible bleeding?
In a concealed abruption the blood is trapped between the placenta and the uterine wall, so the loss is hidden.
Why does placenta praevia cause malpresentation?
The low placenta takes up space in the lower segment and pelvis, so the head cannot engage and the fetus often lies breech or transverse.
Who bleeds in vasa praevia?
The baby: the torn vessels are fetal, so even a small loss can be fatal to the fetus while the mother is not at risk.