Which ultrasound finding would suggest placenta previa?

• A. Placenta implants over the fundus of the uterus
• B. Placenta covering the cervical os
• C. Placenta detaching from the uterus before delivery
• D. Placenta implanted near the umbilical cord insertion

Answer: (B)

Placenta previa is identified on ultrasound when the placental tissue lies in the lower uterine segment and covers the internal cervical os. This placement blocks the opening of the cervix, which is why a placenta covering the cervical os is the hallmark finding. In contrast, a placenta implanted over the fundus is a fundal placenta and not previa, detachment from the uterus before delivery describes placental abruption, and implantation near the umbilical cord insertion points to an abnormal cord insertion, not previa. The key idea is that previa involves the placenta positioned at the lower part of the uterus and over or near the cervical opening, which carries bleeding risk and often necessitates careful delivery planning.