Introduction-Cervical length appears to be an efficient test for predicting preterm birth. Transvaginal sonography (TVS) is the preferred route for cervical assessment to identify women at increased risk of spontaneous preterm birth and may be offered to women at increased risk of preterm birth. Methods-This was prospective observational study conducted in Obstetrics and Gynecology department of SMS Medical college, Jaipur, Rajasthan, Indiafrom August 2015 to July 2016. Out of obstetric cases attending antenatal OPD, cases of singleton pregnancies were selected at random. In this study all the participants were divided into 2 groups: Each group include 100 patients. Every participant underwent a transvaginal sonography (TVS), using probe of 5 to 7.5 MHz, measuring cervical length. Results-About 39 women in control group and 36 women in study group were primigravida, remaining were multigravida. History of preterm labour was present in 27 women in study group and 28 women in control group. Cervical length measurement was 21-26 mm in 30 (30%) women and among them 12 (44.44%) delivered preterm. Mean birth weight was 1.75±0.04 in control group and 1.75±0.06 in study group in which cervical length was between 21-26 mm. In our study in study group revealed Prevalence -27%, Positive predictive value -52.10%, Negative predictive value -88.70%, Sensitivity -81.48%, Specificity -75.34%. Conclusion-We found that TVS had good sensitivity, specificity, predictive value in both group. Thus measurement of cervical length by TVS can be used to predict increase risk of preterm delivery cases with threatened preterm labor.