What is the first test recommended for diagnosing placenta previa?

The first test recommended for diagnosing placenta previa is an ultrasound. This imaging modality is non-invasive and is the gold standard for evaluating the placental location in relation to the cervix. Ultrasound can effectively identify whether the placenta is covering the cervical os, which is critical in diagnosing placenta previa.

Ultrasound is preferred especially in the first and second trimester of pregnancy. It allows for accurate assessment without exposing the mother or fetus to radiation, making it the safest option. Other imaging techniques, such as CT scans and X-rays, expose patients to radiation, which poses risks during pregnancy and are not routinely used for this purpose. A pelvic exam can provide some information, but it is not reliable for diagnosis and can increase the risk of bleeding if the placenta is previa. Therefore, the non-invasive nature and effectiveness of ultrasound make it the appropriate first-line test for diagnosing this condition.