Transvaginal Sonographic SSMC Score to predict successful labour induction: Results from a double-blind prospective study

Abstract

Objective:

Primary objective of the study was to compare an integrated Transvaginal Sonographic score, incorporating parameters—cervical length, funneling, and posterior cervical angle—with the Modified Bishop score in predicting successful labour induction. Secondary objective included comparison of acceptability of both methods as determined by study participants’ perception of pain.

Methods:

All consenting patients underwent baseline evaluation including maternal age, gestational age, BMI, parity, estimated foetal weight, and indication for induction. Transvaginal sonography (TVS) with a 5-7 MHz probe measured cervical length, funneling, and posterior cervical angle to calculate a TVS score named Single-sweep Sonographic Measurements of Cervix (SSMC Score), followed by Modified Bishop Score assessment. Labor induction was performed using intracervical Prostaglandin E2 or E1 analogue as per standard protocol. Successful induction was defined as vaginal delivery within 24 hours; failed induction included caesarean delivery or inability to achieve active labour.

Results:

Total of 100 participants found to be eligible for the study. Postdated pregnancy was the most common indication for Labour induction in present study. Higher Modified Bishop Scores (≥6), cervical length <28 mm, presence of funneling, and PCA > 120° were significantly associated with successful induction. ROC analysis identified cervical length (AUC ~0.80) as the most accurate predictor, slightly outperforming MBS (AUC ~0.77) while Integrated TVS score showed comparable efficacy (AUC~0.77) vis a vis MBS with lesser perception of pain on Visual Analogue scale.

Conclusion:

TVS based SSMC Score is equally efficacious, objective predictor of successful labour induction compared to age-old subjective Modified Bishop’s score with a better acceptability among participants.

Keywords- Transvaginal Sonography, SSMC score, Labour induction, Modified Bishop’s Score