Comparing a Double Dose of Vaginal Progesterone to no Treatment for the Prevention of Preterm Birth in Twins Pregnancy and Short Cervix

Twin pregnancies are more likely to be delivered preterm than singleton pregnancies. Vaginal progesterone administration (200 mg Utrogestan) to asymptomatic women with a singleton pregnancy and sonographic short cervix reduced the risk of preterm birth (PTB) and neonatal morbidity and mortality, yet not proved efficient in twins' pregnancy. The investigators' hypothesis is that a higher dose of vaginal micronized progesterone will be more effective in preventing PTD. The objectives of the study is to compare the rate of preterm birth and perinatal morbidity and mortality in a twin pregnancy with short cervical length treated with vaginal 400 mg of micronized progesterone to no treatment. The study is Randomized, open label, of twin pregnancy between 16-26 weeks of gestation with cervical length under 25 mm. Women will be randomly assigned to either treatment or no treatment group. Progesterone treatment will be given until 36 weeks of gestation. Other management will be according to standard protocol.