Postnatal healing of cesarean scar: an ultrasound study.

Abstract

BACKGROUND Impaired healing of cesarean delivery scars results in long-term complications, including scar niche formation, which may adversely impact future pregnancies and lead to gynaecological symptoms such as postmenstrual spotting, dysmenorrhea and chronic pelvic pain. Moreover, there is increasing evidence that a cesarean delivery scar located close to or within the cervix is associated with an increased risk of subsequent spontaneous preterm birth. The factors influencing cesarean birth scar location and healing remain poorly understood. OBJECTIVE(S) We explored the impact of antenatal, intrapartum, intraoperative and postnatal factors on cesarean scar sonographic healing, location and morphology after cesarean delivery in labor. STUDY DESIGN This prospective observational cohort study recruited women who underwent cesarean delivery during active labor (cervical dilation 4-10 cm) at University College London Hospital, UK (January 2021-October 2022). Transvaginal ultrasound was performed 4 to 12 months postpartum to evaluate cesarean delivery scar characteristics and location relative to the internal cervical os. Indicators of impaired scar healing were presence of a scar niche (depth ≥2mm) and/or a healing ratio (residual/adjacent myometrial or cervical thickness) of ≤0.5. Regression analysis assessed the associations between clinical variables and cesarean scar parameters. RESULTS Cesarean delivery scars were identified in 96.8% of women recruited (90/93). Advanced labor cesarean delivery (8-10 cm dilatation) was associated with an eight-fold increased likelihood of a scar located at or caudal to the internal os (RR 7.77; 95% CI 2.59, 23.39; p<0.001) compared to cesarean birth performed earlier in labor (4-7 cm dilatation). Cervical dilatation and fetal station at surgery significantly influenced scar position relative to the internal cervical os (p<0.001). For each 1cm increase in cervical dilatation during labor, the scar was positioned 0.88mm more caudally on the uterus or cervix (95%CI 0.62, 1.14; p<0.001). Similarly, for each 1cm descent of the fetal part within the maternal pelvis, the cesarean scar was located 1.5mm more caudally on the uterus or cervix (95%CI 0.71, 2.33; p<0.001). The niche prevalence was 37.8% (34/90), of which 67.6% (23/24) had a healing ratio ≤0.5. Risk factors for suboptimal scar healing included BMI ≥ 25, increased uterine artery vascular Doppler resistance, gestational age > 40 weeks, the use of locking sutures during surgery and cesarean delivery scar location caudal to the internal os on postnatal ultrasound (p<0.05). Uterine scars, situated cranial to the internal os, had significantly larger niche dimensions compared to those located within the cervix, at or caudal to the internal os (p<0.05). CONCLUSION(S) Advanced cervical dilatation and low fetal station at emergency cesarean delivery in labor are independent predictors of cesarean scar location near or within the cervix, and these cervical scars heal less well than scars located higher in the uterus. Even women having a cesarean birth at 8-9cm have a high risk of the scar being close or within the cervix, which is known to increase the risk of subsequent spontaneous preterm birth. Further research is needed into the impact of cesarean scar characteristics on gynaecologic symptoms and future pregnancy outcomes and to develop techniques to improve cesarean scar healing.