Short cervix increases risk of preterm birth thirteenfold

In women with uterine anomalies, such as bicornuate uterus, unicornuate uterus, septate uterus, and uterus didelphys, a cervical length of less than 25 mm on transvaginal ultrasonography makes preterm birth 13 times more likely, according to results from a prospective study of 64 women.

Researchers calculated an overall incidence of spontaneous preterm birth at less than 35 weeks of 11%. Of 10 women with a short cervical length, 50% had a spontaneous preterm birth, compared with 4% of the women without a short cervix. The sensitivity, specificity, and positive and negative predictive values of a short cervical length for spontaneous preterm birth were 71%, 91%, 50%, and 96%, respectively (RR 13.5, 95% CI; 3.49–54.74).

Airoldi J, Berghella V, Sehdev H, et al. Transvaginal ultrasonography of the cervix to predict preterm birth in women with uterine anomalies. Obstet Gynecol. 2005;106:553-556.