Prevention of preterm birth in twin pregnancies.

Twins represent 3.2% of all live births; however, they account for 20.0% of all preterm deliveries, with 60.0% and 10.7% of twins delivered before 37 and 32 weeks' gestation, respectively. Twin pregnancies have 5 times higher risk of early neonatal and infant death related to prematurity. Monochorionic twins have a higher incidence of both indicated and spontaneous preterm delivery than dichorionic twins. Transvaginal ultrasound of the cervical length before 24 weeks' gestation is the best tool to predict preterm birth, independent of other risk factors. Among all evaluated therapies to decrease or prevent preterm birth in twin pregnancies, the use of vaginal progesterone in women with a transvaginal cervical length of <25 mm decreased neonatal morbidity, and physical examination-indicated cerclage in women with a cervical dilation of >1 cm showed a significant decrease in preterm birth at different gestational ages and perinatal mortality.