(WEBMD) — A simple test could give pregnant women a better idea of when they'll give birth, researchers say.
Currently, only 5 percent of women deliver on their due date. The study authors said estimates can be off by as much as two or three weeks, early or late.
"Measuring cervical length via ultrasound at around 37 to 39 weeks can give us a better sense of whether a mother will deliver soon or not," senior author Dr. Vincenzo Berghella, director of maternal-fetal medicine at Thomas Jefferson University Hospital in Philadelphia, said in a university news release.
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The cervix begins to soften and change shape as a woman's body prepares for labor.