NEW YORK (Reuters Health) – Data on more than 3500 women indicates that transvaginal sonographic cervical length can predict spontaneous preterm birth in twin pregnancies, researchers report in a June 24th online paper in the American Journal of Obstetrics and Gynecology.

As Dr. Roberto Romero told Reuters Health by email “The length of the cervix — measured with ultrasound — is the most powerful predictor of spontaneous preterm labor/birth in pregnant women with a singleton or twin gestation.”

“Preterm birth is the leading cause of perinatal morbidity and mortality worldwide,” he added, “and affects 12% of all births in the United States. Twin gestations occur in 1-2% of all pregnancies, and the risk of preterm birth in such gestations is 60.4%.”

Dr. Romero of Wayne State University, Detroit, Michigan and colleagues reviewed 16 studies of asymptomatic women and a further 5 in symptomatic women. Meta-analyses were conducted in 15 studies.

“We found,” he continued, “that a cervix of less than 20 mm detected between 20-24 weeks of gestation is a good predictor of spontaneous preterm birth, even in women who have no symptoms whatsoever.”

In asymptomatic women, this gave pooled positive likelihood ratio of 10.1 for birth at less than 32 weeks’ gestation and 9.0 for less than 34 weeks of gestation.

A length of 25 mm or less had a pooled positive likelihood ratio of 9.6 to predict preterm birth at less than 28 weeks