Measurable changes To answer that question, Berghella looked at five studies in which researchers used ultrasounds to measure cervical length of a total of 735 pregnant women.
He found that among the women whose cervix was more than 1.18 inches (3 cm) long at the time it was measured, less than 50 percent of these women delivered within a week.
And during labor, the cervix thins down, or effaces completely, and then opens to allow the baby's head to come out."This is something that is easily implementable tomorrow if people wanted," Berghella told Live Science.Guessing game, waiting game Though most women are given an official due date, it is often just a rough estimate.However, studies have shown that women who have a short cervix, less than 1 inch (2.5 centimeters) long, as measured on ultrasound scans during mid-pregnancy, are at high risk for preterm birth.That made researchers wonder whether similar scans could be predictive during the homestretch of pregnancy.[7 Facts Women and Men Should Know About the Vagina] "The beginning of changes in the cervix happen internally, not externally," Berghella told Live Science.