Premature separation of the placenta: ultrasound finds a retroplacental, marginal or subchorionic haematoma in a minority — so a normal scan does NOT exclude abruption; the diagnosis stays clinical.
Orient first
- Abruption is a clinical diagnosis (pain, bleeding, tender tense uterus, fetal distress); ultrasound sensitivity is low.
- Haematoma echogenicity changes with age: acute clot is iso- to hyperechoic to placenta and easy to miss; it becomes hypoechoic over 1–2 weeks.
- The ultrasound's job is fetal viability, placental site (exclude praevia) and a haematoma if visible.
Acquire the study
- Transabdominal ultrasound with a curvilinear probe; transvaginal only once praevia is excluded; colour Doppler to separate haematoma from placenta and myometrium.
The manoeuvre
- Fetal heart rate and viability first.
- Placental site and lower edge distance to the internal os in mm — exclude praevia.
- Retroplacental area: a heterogeneous lens between placenta and myometrium without colour Doppler flow; measure it in three planes.
- Placental thickness (> 5 cm raises suspicion) and a jello-like jiggle of the placenta.
- Marginal and subchorionic collections at the placental edge.
What confirms it
- A retroplacental or marginal haematoma without Doppler flow in a patient with bleeding or pain.
What licenses you to exclude it
- A normal ultrasound cannot exclude abruption — say it explicitly in the report.
The classic misread
- Calling a myometrial contraction or a fibroid a haematoma — contractions change over minutes and fibroids show flow.
- Reassuring clinicians with a normal scan.