MRI may be effective at ruling out placenta accreta, a potentially life-threatening complication of pregnancy, researchers say.
The test correctly identified 88% of positive cases and 96% of negative cases in about 70 high-risk women, Michele A. Browne, MD, of the University of California San Diego, reported at the Radiological Society of North America meeting.
"MRI is a useful and accurate adjunct to ultrasound for diagnosis of placenta accreta," Brown said. "Women at high risk for placenta accreta, such as those who've had multiple cesarean sections, should undergo ultrasound. And if ultrasound is inconclusive, MRI should be considered."
Placenta accreta is an abnormal attachment of the placenta with invasion into the wall of the uterus. Brown said it usually requires a hysterectomy, and maternal death occurs in 7% of cases.
The incidence of the condition has increased at least 10 times over the last six decades, from about one in 30,000 births in 1950 to one in 2,500, or as frequently as one in 533 births now, according to different estimates.
Browne said this is likely the result of more frequent cesarean sections, because scar tissue in the uterus interferes with a specific layer of the endometrium that involves placental attachment.
Other risk factors involve any kind of uterine surgery, including abortion, as well as maternal age over 35, both of which have increased substantially over the last 60 years.
To measure the efficacy of MRI for detection of placental accreta, the researchers looked at 108 patients who'd had an MRI at their imaging center between 1992 and 2009 and who were suspected to have the condition.
Outcome results were available for 71 of those women.
Overall, Browne said, the accuracy of MRI was 90.1%.
"Early, accurate diagnosis is very important for this condition because it allows for delivery planning, which improves outcome," Browne said.
That includes a scheduled delivery at 36 to 37 weeks and arrangements for sufficient blood products to be on hand because of high blood loss associated with the condition.
Browne noted that after birth, a cesarean-hysterectomy is usually performed because trying to separate the placenta carries a high risk of complications.
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