A 32-year-old G2P1 woman at 38 weeks gestation presents with sudden onset painless vaginal bleeding. She denies abdominal pain or contractions. Fetal heart rate monitoring is reassuring, and the uterus is soft and non-tender on palpation. Her previous pregnancy was uncomplicated. What is the most likely cause of her bleeding?

The correct answer to the question "A 32-year-old G2P1 woman at 38 weeks gestation presents with sudden onset painless vaginal bleeding. She denies abdominal pain or contractions. Fetal heart rate monitoring is reassuring, and the uterus is soft and non-tender on palpation. Her previous pregnancy was uncomplicated. What is the most likely cause of her bleeding?" is Option A: Placenta previa.

The other options — B) Placental abruption, C) Uterine rupture, D) Vasa previa — are incorrect for this USMLE Exam Prep question. As explained above: Painless vaginal bleeding in the third trimester is the classic presentation of placenta previa, where the placenta covers the internal cervical os. Placental abruption typically causes painful bleed…