Vaginal Progesterone 400mg v.s 200mg for Prevention of Preterm Labor in Twin Pregnancies

It is already known that the risk of preterm labor in twin pregnancy before 37 week is 8-9 fold higher compared to singletons, and progesterone supplementation can decrease the incidence of preterm labor in singleton pregnancy. There were studies that used 200mg vaginal progesterone with no effect on the result So this study aims To examine the effect of prophylactic vaginal progesterone 400mg v.s 200mg for prevention of preterm birth in twin pregnancies