Transvaginal Ultrasound Safest for Mother, Fetus.

MARINA DEL REY, CALIF. -- In emergency obstetric situations threatening both the mother and fetus in the third trimester, transvaginal sonography is the best method to evaluate the placenta, the cervix, and their relationship to each other, Dr. Beryl R. Benacerraf said at a conference on ultrasound and women's health.

Safer and more accurate than manual evaluation or translabial ultrasound, transvaginal ultrasound is "uniquely suited" to determine the management of placenta previa, placenta accreta, and vasa previa.

To distinguish between low-lying placentae and an emergency situation after 24 weeks, "transvaginal [ultrasound] is the best way to look at the placenta and its relationship to the cervix. You can never get into trouble using a transvaginal probe to see the placenta," said Dr. Benacerraf, professor of radiology and of obstetrics and gynecology at Harvard Medical School, Boston.

Transvaginal ultrasound is particularly effective in evaluating changes that characterize placenta accreta, another obstetric emergency that can be detected as early as the second trimester, she said at the conference, sponsored by the American Institute of Ultrasound in Medicine.

Placenta accreta is a "real risk" among patients who have ...