Multiple pregnancies accounted for 1 - 6 % of all births in UK during 2007. More than 98% of these multiple births being twin births . Preterm birth defined as birth occurring prior to 37 weeks of gestation and it was about 15 % of pregnancies in developed world and 12.7 % in the United States.

Preterm birth is the leading cause of infant and neonatal mortality. Premature neonates are at increased risk of developing respiratory distress syndrome, sepsis, intraventricular hemorrhage, and necrotizing enterocolitis.

Twin pregnancy is considered one of the important risk factors of preterm birth. Over distension of uterus may be one of the etiological factors for preterm birth. However, no definite effective interventions have been shown to prevent preterm delivery in twin pregnancy.

Three large randomized trials suggested that progesterone might prevent preterm delivery in high-risk singleton pregnancy especially those with previous preterm delivery or short cervix might be reduced by antenatal progesterone.

Fonseca et al (2007) concluded that women with short cervix are less likely to deliver preterm ≤34 weeks if they are treated with vaginal progesterone.

Inclusion Criteria:

1. Diamniotic twin pregnancy
2. Gestational age ± 28 weeks.

Exclusion Criteria:

1. Higher multiple pregnancy
2. IUFD of one or both fetuses
3. Any congenital anomalies
4. IUGR or discordant twins
5. PROM
6. If there is any contraindication to progesterone treatment
7. Women who did performed cervical cerclage in the current pregnancy
8. Difficult in follow up for the pregnant women as (living faraway area, or difficult transportion, etc).
9. Threatened preterm labor.
10. Polyhydromnis.
11. Other medical disorder with pregnancy