Does the appearance of the cutaneous scar after cesarean section reflect the residual myometrial thickness?

PURPOSE: The aim of this study is to utilize the Manchester scar scale (MSS) and ultrasound in investigating the association between uterine wall defects and cutaneous scar characteristics after cesarean section (CS). METHODS: This is a prospective cohort study. The degree of myometrial loss was quantified by calculating a residual myometrial thickness (RMT) ratio as a percentage of RMT to the pre-cesarean anterior uterine wall thickness. Cutaneous scar assessment was performed according to the MSS. Spearman’s correlation and the Kruskal–Wallis test with a cut-off value of p < 0.05 were used for statistical analysis. RESULTS: Two hundred forty seven women, of which 2.4% had an Asian, 3.6% an Afro-American, 82% a Caucasian and 12% a Mediterranean background, were recruited. The RMT ratio ranged between 11.9 and 100% with a median of 55.8% and an average of 56%. MSS scores ranged from 4 to 13 with a median of 5 and an average of 6. Spearman’s correlation between MSS and RMT ratio show a rho of − 0.01 with a p value of 0.8. The correlation between MSS and RMT ratio within the four ethnical groups showed a p value between 0.3 and 0.8 and a rho between 0.8 and − 0.8. The Kruskal–Wallis test showed an eta(2) of 0.13 and a p value of 0.0002 for the effect of ethnicity on MSS and an eta(2) of 0.009 and a p value of 0.68 for the effect of ethnicity on the RMT ratio. CONCLUSION: CS laparotomy scars heal differently between ethnical groups, but generally with satisfying results. Ethnicity does not affect myometrial healing and scar appearance does not reflect myometrial healing after CS. Thus, separate uterine sonographic assessment is recommended.