In a patient with a previous lower segment caesarean section (LSCS), which of the following is the MOST reliable sonographic predictor of uterine rupture in a subsequent trial of labour (TOLAC)?

• A Posterior placental location abutting the scar
• B Bishop score < 6 at onset of labour in TOLAC candidate
• C Non-reassuring fetal heart rate pattern in early active labour
• D Lower uterine segment (LUS) thickness < 2.0 mm on transvaginal ultrasound at 36–38 weeks ✓

Explanation

Lower uterine segment (LUS) myometrial thickness measured by transvaginal ultrasound (TVUS) at 36–38 weeks gestation is the best validated sonographic predictor of scar integrity and risk of uterine rupture in TOLAC. A LUS thickness <2.0 mm (some studies use <2.3 mm) is associated with significantly increased risk of uterine window/dehiscence or rupture during labour. Multiple meta-analyses confirm this threshold. Non-reassuring FHR is an intrapartum predictor, not antenatal. Placental location and Bishop score are not reliable predictors of scar rupture.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.