Understanding Cesarean Scar Morphology: Implications for TOLAC Counseling

An observational cesarean scar morphology study links cervical status at primary cesarean to later scar topography.

This prospective cohort enrolled approximately 92 women undergoing their first cesarean. Their cervical status was documented immediately before the operation, and transvaginal ultrasound was performed three months postoperatively to assess niche presence, width, depth, and myometrial thickness.

Endpoints included niche width and depth, residual and total myometrial thickness, and isolated myometrial defects.

Advanced cervical dilation, effacement, and fetal descent correlated with formation of wider and deeper scar niches (niche width r≈0.59; niche depth r≈0.38). Greater tissue stretch and a lower incision position with advanced labor likely contribute to larger niche formation.

By contrast, limited cervical change at the time of cesarean was associated with a higher frequency of isolated myometrial defects—focal thinning or separation of myometrium without a broad niche cavity. This morphology indicates localized myometrial discontinuity rather than an isthmic cavity and was more common when incision occurred with minimal cervical dilation. Isolated defects therefore convey a distinct morphological risk profile relevant to delivery planning.