Variables influencing the integrity of lower uterine segment in post-cesarean pregnancy

There is significant increase in proportion of cases with previous cesarean delivery requiring obstetric care. The available literature fails to provide uniform opinion on each woman's characteristics to identify risk of uterine rupture while planning trial of labor after cesarean.

To study the association of abnormal lower uterine segment with some of the present and previous obstetric variables including patient characteristics and surgical techniques at previous cesarean operation.

Consenting consecutive 96 post-cesarean singleton pregnancies admitting after 36 weeks gestation at the same facility from July 2011 to December 2012 for repeat cesarean, were studied. Only the cases with cephalic presentation and vertex as presenting part, having no placenta previa, polyhydramnios, uterine anomaly or fibroid and those who had previous one lower segment cesarean were recruited. Based on the intra-operative finding the lower uterine segment (LUS) was categorized into those having a normal and abnormal (grades 2-4) LUS. Sonographic assessment of LUS thickness and any abnormalities if any were noted. The findings of abnormal LUS (direct observation at surgery and sonographic impression within a week before surgery) were looked for association with some of the present and previous obstetric variables including patient characteristics and surgical techniques at previous cesarean operation using Student t, Chi square or Fisher's exact test for analysis as appropriate. Receiver operating curve analysis was used to determine the optimal cut off value for prediction of LUS integrity by ultrasound.

Of the women recruited for the study, 36 were admitted in early labor and ultrasound evaluation of LUS was performed in 48 of the remaining 60 women admitted antenatal for elective cesarean delivery. There were 38 abnormal LUS (39.6%) with 22 of them (57.9%) graded as 'thinned out LUS'. The incidence of scar dehiscence (grade 3, cases 5) was 5.2% of 96 cases and there were no cases of scar rupture. Proportion of cases with abnormal LUS was significantly high when primary cesarean was done in preterm (p = 0.02); it was a single layer uterine closure (p = 0.02), and inter-cesarean interval was 54 months (p = 0.01). Abnormal LUS was also seen to be associated with maternal age beyond 35 years (p = 0.2), when cesarean was performed in labor (p = 0.5), following 18 h of rupture of membranes (p = 0.75), for a baby weight more than 3 kg (p = 0.4), and different suture materials (polyglactin 910 and chromic catgut) were used to close uterus at primary cesarean delivery (p = 0.1), and also if they had post-partum fever (p = 0.3). Ultrasound measurement of LUS by abdominal scan correlated with the intra-operative LUS grading and a thickness of more than 3.2 mm within a week before delivery and was seen to be the safe cut off above which most of the women had a normal LUS (sensitivity 92.3%, specificity 81.1%).

Factors at primary cesarean operation significantly influence the state of LUS at term in subsequent pregnancy .