Short cervical length measured by transvaginal sonography is the one of the best predictor of preterm birth. A cervical length of less than 25 mm between 16 and 24 weeks is known as the reliable threshold for an increase risk of preterm birth in all populations including singleton and multiple gestations, women with or without risk factors for preterm birth, asymptomatic women, as well as those with preterm labor or preterm premature rupture of membranes. Furthermore, measurement of cervical length is a readily learned skill for obstetrical sonographers and transvaginal ultrasonography is acceptable to pregnant women and does not cause discomfort in the vast majority. However, the measurement of cervical length is not yet recommended as routine screening method, especially for those who are at low risk for preterm birth, because there are insufficient treatment methods to prevent preterm birth once short cervix is diagnosed. Recently, not a few researches on short cervix have been focused on the development of treatment strategy. In this article, we will review relevant studies and recent advances in the use of cervical length in the prediction of preterm birth and clinical application including the use of cervical cerclage.