Correlations between sonographically measured and actual incision site thickness of lower uterine segment after repeated caesarean section

Aim. The aim of the present study was to verify how much the sonographically measured thickness of the lower uterine segment caesarean section (LUS-CS) scar correlates with incision site thickness in a repeated caesarean section after uterotonic administration. Methods. Sixty-three obstetric patients at term undergoing repeated caesarean section. LUS-CS thickness was measured sonographically before the repeated caesarean. Some seconds after delivery of the fetus and placenta and administration of an institutional, standard uterotonic, LUS was measured on the site of surgical incision (upper side and lower side) using Castroviejo's caliper. Multiple measurements were taken and averaged for improving accuracy. Mean measurements were used for calculations (unilinear correlations and multilinear regression analyses.). Results. Poor correlation was found between sonographically measured scar thickness and lower uterine side incision thickness (r 0.311; C. I. 95% 0.068-0.519; P=0.013) and between sonographically measured scar thickness and uterine scar overall incision thickness (mean of upper side and lower side measurements) (r 0.254; C. I. 95% 0.007-0.472; P=0.045). Sonographically measured scar thickness was smaller in patients with two or more previous caesareans (P=0.045) and greater in patients who had undergone the last of the previous caesarean sections longer than two years earlier (P=0.043). Patients with two or more previous caesareans had smaller upper-side incision thickness (P=0.005); smaller lower-side incision thickness (P=0.038); smaller incision site overall thickness (P=0.006). Conclusion. Sonographically measured thickness and incision site thickness of the LUS-CS scar are poorly correlated (about 25%), despite the fact that patients most at risk for uterine rupture have thinner LUS, both sonographically and when measured during surgery.