Effect of cervical changes on the cesarean scar topography after primary cesarean sections: an observational study

The increasing global rate of cesarean sections (CS) has raised concern about associated long-term complications, particularly uterine scar niches. A niche represents a localized myometrial defect at the hysterotomy site, which may lead to abnormal bleeding, pelvic pain, or subfertility.

to assess the scar area, niche formation and isolated myometrial defect creation after CS in women undergoing their 1st CS at various stages of 1st stage of labor, irrespective of gestational age.

This prospective observational cohort study was conducted at Ain Shams University Maternity Hospital between April 2024 and February 2025 and included 92 women who underwent their first CS for different obstetric indications at various stages of 1st stage of labor. Cervical changes were recorded just before the cesarean section, then all patients were recalled for TVUS three months postoperatively to evaluate scar location, the presence of a niche or isolated myometrial defect, and residual and total myometrial thickness.

Among the 92 enrolled women, scar-related abnormalities were closely linked to cervical and fetal labor characteristics rather than general maternal or operative factors. While maternal age, BMI, gestational age, fetal weight, operation time, and blood loss showed no significant differences between women with and without niches or isolated myometrial defects (p > 0.05 for all comparisons), cervical dilation (6.0 ± 2.3 cm vs. 4.1 ± 1.9 cm), effacement (58.2 ± 24.4% vs. 36.6 ± 24.4%), and advanced fetal station (0 or + 1 in 67.6% of niche cases) were significantly associated with niche formation (p < 0.001 for all). Niche width and depth correlated positively with cervical dilation (r = 0.591, 0.385; respectively), effacement (r = 0.547, 0.381; respectively), and fetal descent (r = 0.766. 0.545; respectively) (p < 0.05 for all), Conversely, isolated myometrial defect were more frequent in CS performed at less progressive cervical changes and higher fetal head station. Anatomically, niches were more frequent in isthmic scars (55.9%), whereas isolated defects predominated in corpus scars (52.0%). Collectively, these findings suggest that advanced cervical changes contribute to wider and deeper niches, whereas insufficient cervical remodeling favors isolated defects development.

Advanced cervical changes contribute to wider and deeper niches, whereas insufficient cervical remolding favors isolated defect development. Therefore, labor dynamics represent a pivotal determinant of cesarean scar healing and postoperative uterine integrity.