Question 1 · Medium
A 30-year-old third gravida at 33 weeks comes to casualty after waking up in a pool of painless, bright red vaginal bleeding. Pulse is 92/min and BP 116/74 mm Hg; the uterus is soft and non-tender, the presenting part is high and the fetal heart rate is 144/min. The bleeding has now settled. What is the investigation of choice to locate the placenta?
- ADigital vaginal examination
- BTransabdominal ultrasonography
- CMRI of the pelvis
- DTransvaginal ultrasonography
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Answer: D · Transvaginal ultrasonography
Painless, causeless, recurrent bright red bleeding with a soft uterus and a high presenting part suggests placenta previa. Transvaginal ultrasound is the investigation of choice: it measures the distance from the placental edge to the internal os more accurately than the abdominal route, and it is safe because the probe stays in the vagina at an angle to the cervix. A digital examination is avoided because it can provoke torrential bleeding, and is done only in theatre with a double set-up. As she is stable at 33 weeks she is managed expectantly, with corticosteroids, blood kept ready and anti-D if she is Rh negative.
- A: Digital examination can start torrential bleeding in placenta previa.
- B: Abdominal scanning is less accurate, especially for a posterior placenta.
- C: MRI is used to assess suspected placenta accreta, not first-line localisation.