Placenta-Cervical Interface Angle for Predicting Placenta Accreta Spectrum Severity

Overview

Placenta accreta spectrum (PAS) is associated with substantial maternal and neonatal morbidity, and accurate antenatal prediction of its severity remains challenging. Although several sonographic markers exist, most are subjective and operator-dependent, and few predict surgical complexity or adverse perinatal outcomes. This prospective observational cohort study evaluates the Placenta-Cervical Interface Angle (PCIA), a novel geometric transvaginal ultrasound marker, defined as the angle between the longitudinal axis of the cervical canal and the tangent line drawn to the lower placental edge. The study assesses the predictive performance of the PCIA for severe PAS and its association with intraoperative morbidity and adverse perinatal outcomes.

Pregnant women with placenta previa or an anteriorly located low-lying placenta followed at the Perinatology Clinic, Necmettin Erbakan University Faculty of Medicine, will be enrolled prospectively. Using transvaginal ultrasonography in the sagittal plane, the Placenta-Cervical Interface Angle (PCIA) will be measured as the angle formed between the longitudinal axis along the cervical canal and the tangent line to the lower placental edge. All measurements will be performed with an empty bladder in the lithotomy position using a Voluson 8 ultrasound system within the same gestational-age window. Classic sonographic PAS markers will also be assessed, including placental lacunae, bridging vessels, loss of the clear zone, myometrial thickness, bladder-wall invasion, and cervical length. Demographic and clinical variables (age, BMI, gravidity, parity, smoking, IVF versus spontaneous conception, prior cesarean and other uterine surgery) will be recorded. Surgical and perinatal outcomes, including operative time, estimated blood loss, red-blood-cell transfusion, intensive-care requirement, hysterectomy, and neonatal outcomes, will be recorded. To assess reproducibility, a second operator will repeat the measurement in approximately 20% of participants and the intraclass correlation coefficient (ICC) will be calculated. Data will be analyzed with SPSS. The predictive performance of the PCIA for severe PAS and adverse perinatal outcomes will be evaluated by ROC analysis, with the optimal cut-off determined by the Youden index; sensitivity, specificity, and positive and negative predictive values will be calculated. Multivariable logistic regression will be used to identify independent predictors. A p-value below 0.05 will be considered statistically significant.