Objective: To identify histological determinants (uterine scar specifics) of trial of labor after cesarean section (CS). Materials and methods: This prospective study was conducted in 2013–2019 in Moscow maternity hospitals No. 68 and No. 29. The study included 272 women who wanted to have vaginal delivery but underwent CS. Of them, 182 underwent prelabor CS (vaginal delivery was either not considered or not attempted), and 90 had intrapartum CS (vaginal delivery was attempted but converted to CS). Results: Scar histology was correlated with a combination of highly diverse clinical, anamnestic, and maternal ultrasound factors. They included number of years lived, age of menarche, pre-pregnancy body mass index (BMI), number of phenotypic manifestations of undifferentiated connective tissue dysplasia, ordinal number of deliveries, interval between previous CS and present pregnancy, estimated fetal weight, amniotic fluid index, minimal scar thickness, right uterine artery resistance index before labor (Wilks' Lambda=0.006, p<0.001). In the attempted trial of labor, the predominance of fibrous tissue was associated with a lower age of menarche, higher prepregnancy BMI, and fifth-minute Apgar score. Conclusion: Myometrial reparation after CS characterizes the body as a whole. The histology of the uterine scar after CS combines prepregnancy, gestational, and intrapartum factors beyond those that were surgically determined. Myometrium histology is not an argument for post factum justifying or challenging attempted trial of labor: the prevalence of muscle tissue, muscle tissue with foci of fibrosis, or fibrous tissue is comparable. © A group of authors, 2022.