RecruitingProspective Evaluation of Pathways for Preterm BirthThis is a single center, prospective cohort study of pregnant patients at high risk for spontaneous preterm birth: patient's with history of spontaneous preterm birth, patient's with a short cervix and patient's symptomatic for preterm birth will be included. A control cohort of nulliparous patients without a short cervix will be recruited to provide baseline data. Plan to enroll 240 patients identified through our ultrasound unit with goal of 60 patients in each group.