Direct Measurements of Cervical Remodeling for Predicting Preterm Birth

Inclusion Criteria: * All pregnant women screened at \< 18 weeks with a documented singleton pregnancy, who agree to participate in the study (group 1). A subset of Nulliparous women (no previous pregnancy 15 weeks)(group 2) will be assessed. * Women of all races and age will be included. Exclusion Criteria: * Women with a multi-fetal pregnancy, current use of systemic steroids or immunosuppressive therapy or enrollment for prenatal care after 24 weeks. * Women with a prior documented history of Leep or Conization will be excluded. * Any known Mullerian anomalies such as septate uterus, bicornuate or unicornuate uterus will be excluded given that these are high risk groups for preterm delivery.