Gestational context
20 to 40 weeks
Maternal
- Haemodynamics
- heart rate first, then blood pressure
- Abdomen
- soft (praevia) or tense and tender (abruption)
- No digital examination until placental site is known
- No digital examination until placental site is known
- Anti-D if Rh negative; Kleihauer
- Anti-D if Rh negative; Kleihauer
Fetal
- Heart rate on the monitor from arrival
- Heart rate on the monitor from arrival
- Presentation and placental site on ultrasound
- Presentation and placental site on ultrasound
- Abruption is diagnosed clinically, ultrasound misses most
- Abruption is diagnosed clinically, ultrasound misses most
- Delivery timing by maternal and fetal stability
- Delivery timing by maternal and fetal stability
The three placental causes
| Placenta praevia | Abruption | Vasa praevia |
|---|---|---|
| Placenta covers the internal os (low-lying: within 2 cm) | Placenta separates before delivery | Fetal vessels run through the membranes over the os |
| Painless bright bleeding, often recurrent, uterus soft | Painful, uterus tender and hard, may be concealed; bleeding may be small | Bleeding at rupture of membranes; fetal, so the fetus collapses fast |
| Diagnosed on the anatomy scan and re-scanned at 32 weeks; transvaginal scan is safe | Clinical diagnosis; ultrasound misses most | Antenatal transvaginal colour Doppler; suspect with velamentous insertion, succenturiate lobe, low placenta |
| Risk: prior caesarean, prior praevia, multiparity, smoking. Accreta spectrum when praevia sits on a scar | Risk: hypertension, trauma, cocaine, smoking, prior abruption, PPROM, sudden decompression | Delivery by planned caesarean at 34 to 36 weeks before the membranes rupture |
Normal central placental cord insertion, three-vessel cord
Transabdominal with colour Doppler, 20+4 weeks. Central cord insertion into the placenta.
Open in the Ultrasound LabAssessment
- 1
Maternal stability first
Two large-bore cannulas, CBC, group and screen or crossmatch, coagulation, Kleihauer if Rh negative. Estimate loss; remember concealed abruption bleeds into the uterus.
- 2
Fetal status
Continuous monitoring. Abruption gives a hypertonic uterus with contractions on the toco and a fetal heart rate that deteriorates.
- 3
Where is the placenta?
Check the last scan before anyone examines. Speculum is acceptable once praevia is excluded; digital examination with a praevia can provoke catastrophic bleeding.
- 4
Decide
Major bleeding, maternal instability or fetal compromise: deliver (caesarean for praevia, and usually for abruption unless delivery is imminent). Minor bleeding with a stable mother and fetus: admit, observe, steroids if preterm, anti-D if Rh negative.
Placenta accreta spectrum
A placenta that invades the myometrium (accreta, increta, percreta) sits on the far end of the praevia-on-a-scar story. It is suspected on ultrasound (lacunae, loss of the retroplacental clear space, bladder wall interruption) and MRI, and delivered by a planned caesarean at 34 to 36 weeks in a centre with blood bank, interventional radiology and surgical support, usually leaving the placenta in place and proceeding to hysterectomy.
Check
33 weeks, painless bright red bleeding of about 150 mL, the uterus is soft, the fetal heart rate is normal. The anatomy scan is not in the notes. What is the correct examination?
On the modelPlacentaIsthmus and lower segmentCervix