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

Inclusion Criteria:

1. Primigravidae
2. Twin pregnancies at gestational age 14 week.
3. Cervical length more than 2 cm (because if 2cm or less they will undergo cervical cerclage.)

Exclusion Criteria:

• Polyhydramnios
• Anemia
• Twins with congenital malformation
• Twin to twin transfusion
• Medical diseases as diabetes mellitus, hypertension and systemic lupus erythematosis
• Previous cervical surgery
• High order pregnancy (triples or more)