Role of Ultrasonography in Measuring the Scar Thickness in Cases of Previous Lower Segment Caesarean Section

Introduction - The frequency of caesarean section in the world is increasing being the most common surgical procedure in obstetric health care services. It is the reason for serious concern and demands immediate international attention. While vaginal births after Caesarean (VBAC) are not uncommon today, the rate of VBAC has declined to include less than 10 % of births after previous caesarean section due to concerns regarding the potential catastrophic effect of uterine rupture. Aims and objectives - This study was undertaken to evaluate the role of ultrasonography in detecting the thinning of lower uterine segment scar to decide the technical management of subsequent delivery in cases of previous LSCS and in predicting the risk or intrapartum uterine scar dehiscence. Materials and methods - 200 patients admitted in the labour room emergency of NALANDA MEDICAL COLLEGE AND HOSPITAL, Patna between September 2010 to July 2012 and had elective/emergency repeat caesarean section for various indications were included. Clinical, ultrasonographic and per operative findings of scar thickness and its integrity were compared. Results - The mean thickness of lower uterine segment in the patients with scar defects was 2.11+.93 mm and in patients with intact scar was 3.29+ 0.87 mm. the difference being highly significant (P4.5mm, 2 of the 81 patients (2.41 %) with values 3.6-4.5 mm, 10 of 58 patients (17.24 %) with values 2.5-3.5 mm, 12 of 38 patients (31.59 %) with values 1.6-2.5 mm and in all 16 women. Prediction of scar rupture by ultrasonography taking a cut off value of 3.5mm of scar thickness was 90 % sensitive, 52 % specific, positive and negative predictive value being 31.2 % and 95.5 % respectively. Conclusion - Ultrasonographic examination of the lower uterine segment in cases with previous caesarean sections was found to be useful in assessment of scar integrity. Lower segment scar measuring more than 4.5mm were found to be intact and those measuring less than 1.6 mm always dehiscenced. Hence it is concluded that all patients with less than 1.6mm lower segment scar thickness should undergo elective caesarean section and with measurements greater than 4.5 mm should be allowed trial for vaginal delivery.