OP15.06: Sonographic assessment of uterine Caesarean scar healing

To explore the relationship between maternal and peripartum factors and Caesarean scar sonographic appearance within the first year postpartum. This ethically approved prospective observational cohort study included women who underwent emergency Caesarean delivery during labour (cervical dilatation 4-10cm) at University College London Hospital (Jan 2021-Oct 2022). A transvaginal ultrasound scan at 4-12 months postdelivery assessed Caesarean scar position and presence of sonographic indicators of poor healing, including niche development (an indentation at the scar site ≥2mm) and healing ratio (residual myometrial thickness/adjacent myometrial thickness) ≤ 0.5. Scar position was assessed in relation to the internal cervical os. Multivariate logistic regression analysis was used to assess the impact of significant factors identified in univariate analysis. Caesarean scars were visualised in 97% (90/93) of women, with niche formation in 38% (34/90) and a healing ratio of ≤ 0.5 in 26.7% (24/90) of women. There was a significantly higher proportion of scar niches and low healing ratios when scars were at or below the internal os compared to lower segment scars (50% vs 29%, p = 0.04 and 42% vs 15%, p = 0.005, respectively). Uterine hypoperfusion (defined as second trimester combined uterine arteries pulsatility index >2.5), birthweight >4000g and scar at or below internal os were significantly associated with an increased risk of niche development (OR 39.2, 95%CI 2.3-661.0, p = 0.011; OR 9.2, 95%CI 1.3-63.8, p = 0.024 and OR 8.2, 95%CI 1.6-40.9, p = 0.010; respectively) and reduced healing ratio (OR 61.2, 95%CI 4.3-873.4, p = 0.002; OR 14.8, 95%CI 2.3-95.8, p = 0.005 and OR 9.8, 95%CI1.6-58.2, p = 0.012; respectively). Caesarean scars located at or below the internal of are significantly more likely to heal poorly compared to lower segment scars. This may potentially compromise the cervical support function in subsequent pregnancies leading to spontaneous preterm birth.