Evidence regarding efficacy of interventions designed to prevent preterm birth has been disappointing. Most well-designed clinical trials have failed to demonstrate any reduction in preterm births with such interventions as home uterine activity monitoring, reduced physical activity, administration of antibiotic or tocolytic therapy, and intensive and frequent antenatal follow ups. Recently, progesterone has shown some promise in the prevention of preterm birth among women with prior preterm births. Whether this intervention will prove effective in other populations, such as women with multiple gestations, remains to be seen.