Vaginal Progesterone for the Prevention of Preterm Birth in Twins

Overview

This trial is a randomised, multi-centre, 2 x 2 factorial designed pilot trial with two factors of 200mg vs. 400mg progesterone self-administered daily from 11-14 weeks' gestation vs. 20-24 weeks' gestation, to compare the median gestational age (in days) at delivery between the comparison groups.

Randomised studies in singleton pregnancies suggest that the risk of preterm birth can be decreased by using of progesterone. However, in twin pregnancies, no significant reduction in preterm birth has been demonstrated in any trial. One explanation for the lack of benefit of progesterone in previous twin studies may result from a suboptimal dosage. The investigators therefore hypothesize that progesterone dosages that are sufficient for singleton pregnancies are insufficient for twins and this is likely to be one of the reasons why prophylactic progesterone has failed to reduce preterm birth in twins. Another possible explanation for the negative findings in previous twin studies may result from administration beginning too late in the second-trimester. It is thought that the mechanism of preterm birth in twin pregnancies is more strongly related to exaggerated uterine distension, which may override any benefit of progesterone on the cervix after a threshold has been reached. It is also plausible that cervical shortening occurs earlier in twin pregnancies than with singletons, and that treatment is required before a threshold of shortening is reached or before any inflammation-mediated component to the initiation of preterm birth has been established as the biological mechanisms by which preterm birth occurs differ from those in singleton pregnancies.

Conditions

Interventions

Eligibility

Locations (4)

Outcomes