Antepartum Hemorrhage and Suspected Placenta Previa
A 30-year-old G2P1 at 36 weeks of gestation has had painless bright red vaginal bleeding for 1 day, soaking two pads. The uterus is soft and non-tender, the lie is transverse, and the presenting part is high. Blood pressure is 118/70 mm Hg and pulse is 92 beats/min. Cardiotocography is normal. Which of the following is the most appropriate next action?
- A.Transabdominal ultrasound for placental localizationCorrect
- B.Digital vaginal examination of the cervix
- C.Oxytocin contraction stress test
- D.Fetal auscultation with a DeLee stethoscope
Explanation
Painless bright red bleeding in the third trimester with a soft non-tender uterus and an abnormal lie is placenta previa until proven otherwise. The low-lying placenta occupies the lower segment, preventing engagement and predisposing to transverse or oblique lie, and bleeding occurs as the lower segment forms and the placenta shears away. Ultrasound, transabdominal first and transvaginal if needed for precise localization, is the safe and definitive investigation; transvaginal scanning is safe in previa because the probe is directed at the anterior fornix and not through the cervix. A digital vaginal examination is absolutely contraindicated before previa is excluded because the examining finger can disrupt the placenta and provoke catastrophic hemorrhage. Placental abruption is the main differential but classically causes painful bleeding with a tense tender uterus and often fetal compromise, neither present here. A contraction stress test deliberately induces contractions, which is dangerous with an undiagnosed previa. A DeLee stethoscope only auscultates the fetal heart and yields no information about the source of bleeding. Alongside imaging, management includes intravenous access, blood group and crossmatch, anti-D if the mother is rhesus negative, corticosteroids if preterm delivery is anticipated, and admission.
Why each option
- A.
- Correct. Ultrasound localizes the placenta safely and confirms or excludes previa before any vaginal examination is contemplated.
- B.
- Digital vaginal examination is contraindicated in undiagnosed antepartum hemorrhage because it can provoke torrential bleeding from a placenta previa.
- C.
- Inducing contractions in a woman who may have placenta previa risks major hemorrhage and provides no diagnostic information about the bleeding source.
- D.
- Auscultation confirms fetal life but identifies neither the cause nor the severity of the bleeding, and cardiotocography has already been performed.
Reference: RCOG Green-top Guideline No. 27a, Placenta Praevia and Placenta Accreta, 2018, reaffirmed 2023
This is one of 3,306 questions in the MedBoardSA SMLE bank, with timed test mode, tutor mode, and progress tracking by topic.
Practise the full bank