Preterm birth is defined as the birth of a baby during the gestational weeks of 28 to 37. At present, preterm birth is diagnosed according to the clinical information, such as high risk factors, uterine contraction, and cervical bishop score and so on. Recent years, ultrasonic monitoring of cervical length and detection of specific indictors of cervical vaginal secretions, for example fetal fibronectin, placental alpha-microglobulin 1, inflammatory cytokine and insulin-like growth factor-binding protein-1 and so on, were taken advantage to predict preterm birth, which captured eyes of scholars. The authors discuss new ideas about prediction of preterm birth.