The goal of our research will be to determine the effectiveness of 17 alpha-hydroxyprogesterone caproate (17P) in the treatment of preterm delivery. Treatment with progesterone is emerging as the standard of care for prevention of preterm delivery in asymptomatic patients at high risk for preterm birth due to a prior preterm delivery. Our goal is to evaluate whether or not progesterone is also effective in reducing preterm birth in symptomatic patients.