Preterm birth is one of the leading causes of neonatal morbidity and mortality. One of the greatest predictors of preterm birth is a history of prior spontaneous preterm birth. Presently 17 hydroxyprogesterone caproate (intramuscular) is the only FDA approved product for the prevention of recurrent preterm birth, however recent studies suggest that vaginal progesterone may be used for this purpose, and may even be superior. The American College of Obstetrics and Gynecology does not specify the optimal route of progesterone administration for the prevention of recurrent preterm birth. It is our intention to compare vaginal and intramuscular progesterone to see if one is superior.