Cervical Length Versus Modified Bishop’s Score for Prediction of Successful Labor

Background: Bishop’s score is a subjective scoring system, investigators tried to find another way to objectively predict the success of labor induction. Aim: The aim of this study is to compare the cervical length (CL) measured by transvaginal ultrasound (TVS) versus modified Bishop’s score for predication of successful labor induction in nulliparous women. Subjects and Methods: A total of 210 nulliparous women admitted with premature rupture of membranes for induction of labor included in this comparative prospective study conducted in Ain Shams University, Department of Obstetrics and Gynaecology from February 2013 to February 2015. Studied women examined by TVS for measurement of CL and vaginally to calculate the modified Bishop’s score, followed by induction of labor. Collected data analyzed using the independent Student’s t-test, and Chi-square tests of Statistical Package for Social Sciences, (Chicago, IL, USA). Outcome measures; success of induction process defined as vaginal birth after induction and duration of labor induction. Results: One hundred and forty-three women of studied women had CL <28 mm; 76.25% (122/160) of them delivered vaginally and 21 delivered by cesarean section (P 0.03). One hundred and forty-six women of studied women had modified Bishop’s score >4; 80% (128/160) of them delivered vaginally and 18 delivered by cesarean section (P 0.006). Out of 67, 38 women had CL ≥ 28 mm delivered vaginally, and this difference was statistically significant (P 0.002). The CL <28 mm was significantly more specific with more positive predictive value (PPV) as the predictor of successful labor induction (86.25% and 61.4%, respectively) compared to modified bishop’s score (50% and 23.8%, respectively), (P 0.007 and P 0.001; respectively). Induction to delivery time was significantly less in women with CL <28 mm compared to women with CL ≥ 28 mm (8.5 [5.2]. vs. 15.2 [6.4]h, respectively) (P 0.02, 95% confidence interval [CI].; 4.9, 6.7, 8.4). Women with modified Bishop’s score >4 had significantly less induction to delivery time compared to women with modified Bishop’s score of ≤ 4 (7.7 [4.25] vs. 10.8 [5.30] h, respectively) (P 0.01, 95% CI; 1.6, 3.1, 4.5). Conclusion: CL <28 mm measured by TVS was significantly more specific with more PPV compared to modified bishop’s score in prediction of successful induction of labor. Both CL measured by TVS and modified bishop’s score were complementary tool and associated with successful induction. Keywords: Cervical length; Labor induction; Modified Bishop’s score

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