Vaginal bleeding is less common during the second and third trimesters of pregnancy than during the first trimester. There are many different causes for vaginal bleeding during pregnancy. Bleeding can be normal. In about half the cases, the reason for the bleeding is never found. However, the bleeding may be caused by something serious for either the mother or the baby. Imaging with ultrasound is the most accurate way to determine the reason for vaginal bleeding during pregnancy.
Transabdominal ultrasound (performed using a probe on the outside of the body, through the lower abdomen) is usually appropriate for evaluation of bleeding with or without pain during the second and third trimesters. Transvaginal ultrasound (performed using a probe inside the vagina) is appropriate and may be used to evaluate the cervix and the placenta. Ultrasound with Doppler (to look at blood vessels) is also appropriate. Two or three of these tests may be performed together during the same examination. Transperineal ultrasound (performed with the probe on the outside of the vagina) may also be appropriate.
Possible causes of bleeding during the second and third trimester include placenta previa (placenta crosses the cervix), low-lying placenta (placenta is close to the cervix), and vasa previa (blood vessels to the umbilical cord cross the cervix). When doctors suspect these problems, transabdominal ultrasound, transvaginal ultrasound, and ultrasound with Doppler are usually appropriate. Two or three of these tests may be performed together during the same examination.
For more information, see the Abnormal Vaginal Bleeding page.
— By Samantha Greben, BA and Nina S. Vincoff, MD. This information originally appeared in the Journal of the American College of Radiology.