By Steven Reinberg
WESTPORT, CT (Reuters Health) – For women who have had a previous spontaneous preterm delivery, a short cervix length in the midtrimester is predictive of spontaneous preterm birth, according to a report in the September 19th issue of the Journal of the American Medical Association.
In a multicenter study, Dr. John Owen from the University of Alabama at Birmingham and colleagues collected data on 183 women with singleton pregnancies who had had a spontaneous preterm birth before 35 weeks' gestation. Using vaginal ultrasound, the women were screened during the midtrimester at 2-week intervals.
While a shortened cervix was present in some women early in gestation, it developed over time in others, which is why serial screening is important, Dr. Owen told Reuters Health.
Among the 183 women, 48 had a spontaneous preterm birth before 35 weeks gestation. A cervical length of less than 25 mm on the initial sonograph was associated with a relative risk of 3.3 for preterm birth. When cervical length of less than 25 mm was also seen on serial sonograms, the relative risk for preterm birth increased to 4.5, the researchers note.
"We also looked at funneling and we found that women with funnels tended to have a shorter cervix," Dr. Owen said. But when we controlled for cervical length, whether there was a funnel there or not it didn't seem to matter. It's the shortness that's bad, not the funneling," he concluded.
The study was limited to the midtrimester, because if a shortened cervix is suggestive of cervical incompetence, it might be treatable with such things as a cerclage, Dr. Owen said. "Our goal is to perform a randomized clinical trial of cerclage in women who have a short cervix in the midtrimester. Until we have that information, it will be difficult to use the information from vaginal ultrasound wisely," he added.
"Right now, screening women with vaginal sonography should not become a standard of care, at least until we know if there are any interventions that might be effective," Dr. Owen said.