Preterm birth remains a leading cause of perinatal mortality and morbidity. Despite advances in obstetric and pediatric care, the incidence of preterm birth has increased by more than 20% in the last two decades. Approximately 12.8% of births are preterm, however these account for more than 75% of all perinatal morbidity and mortality. Currently prophylactic progesterone administration is the most effective method available for the prevention of recurrent preterm birth. Prior studies have examined the impact of progesterone in women with recurrent preterm birth and cervical shortening. The possible use of progesterone in women experiencing active preterm labor may address the highest risk condition, however, there have not been any clinical trials to date examining this use of vaginal progesterone. Inflammation and decidual hemorrhage are among the proposed mechanisms that appear to be related to preterm labor.We will use a double blinded randomized drug placebo design to study the proposed outcomes in women diagnosed with preterm labor and planned to have standard of care tocolytic therapy. Women will be randomized to daily vaginal progesterone gel or placebo and will be maintained on the drug or placebo until delivery or 36 6/7 weeks.