Which imaging modality is preferred to locate placenta previa?

• A. CT scan
• B. MRI
• C. Pelvic ultrasound
• D. Transabdominal ultrasound

Answer: (D)

Placenta previa is diagnosed using ultrasound because it safely shows the placental edge in relation to the internal cervical os without exposing the fetus to radiation. The initial imaging approach is transabdominal ultrasound, which provides a broad view of the uterus and can identify placenta previa in many cases. It’s widely available, fast, and noninvasive, making it the preferred starting test to locate the placenta. If the transabdominal view is inconclusive or if precise localization is needed—such as to plan delivery or assess the edge relative to the os—transvaginal (pelvic) ultrasound offers higher resolution and is used to confirm the exact position. CT is avoided in pregnancy due to radiation exposure, and MRI isn’t routinely required for locating placenta previa, being reserved for more complex placental pathology when ultrasound results aren’t clear.