Materials and Methods: We conducted a prospective study in 128 pregnant women admitted to Bhumibol Adulyadej Hospital between December 2014 and July 2016 and received the treatment for induction of labor. All patients were measured for CL using transvaginal ultrasonography [TVUS] followed by pelvic examination for BS assessment. Primary outcome was reliability of CL and BS to predict the risk of cesarean delivery. Secondary outcome was pain score derived from both techniques.

Results: Sixty patients underwent cesarean section. Of these, there were 54.8% of patients with CL greater than 2 cm, and 63% of patients with BS of 5 or less. Regarding to prediction of cesarean delivery, CL had a higher sensitivity (85%, 95% CI 79 to 94) than BS (76.7%, 95% CI 66 to 88). We also found that TVUS for CL measurement had a lower pain score than BS assessment using pelvic examination (1.37 vs. 4.20, p = 0.0001).

Conclusion: CL derived from TVUS had a higher sensitivity to predict the risk of cesarean delivery and had a lower pain score compared to BS assessment using pelvic examination.

Keywords: Induction of labor, Cervical length, Bishop score