Screening for preterm birth in twin pregnancies.

Twins represent 3.2% of all livebirth. However, they account for 20% of all preterm deliveries, with 60% delivering before 37 weeks, and 10.7% before 32 weeks. Twin pregnancies have five times higher risk of early neonatal and infant death related to prematurity. Monochorionic twins have higher incidence of both indicated and spontaneous preterm delivery compared with dichorionic twins. Additional risk factors include history of preterm delivery and cervical surgery. Transvaginal cervical length before 24 weeks is the best tool to predict preterm birth, independent of other risk factors.