Scoring system for the prediction of the severity of placenta accrete spectrum in women with placenta previa: a prospective observational study

Purpose The clinical outcomes are significantly different in accreta, increta, and percreta. There is currently no scoring system that can preoperatively distinguish its severity in an at-risk population. The aim of this study is to establish a scoring system for the prediction of the severity of placenta accrete spectrum (PAS) in women with placenta previa. Methods A prospective observational study was conducted in patients with placenta previa who delivered at a Chinese tertiary care center between June 12, 2016 and June 30, 2018. Optimal scaling regression was performed to determine the parameters which really contribute to the prediction of PAS, and calculate percentage of contribution. Results Among 392 cases with placenta previa, 79, 53, and 28 had been surgically and/or histologically confirmed as accreta, increta, or percreta, respectively. Seven parameters were scheduled for the estimated scores for PAS, and five of them were finally entered into the predictive model. Their percentage of contribution was as follows: placental lacunas (19%), vascularity at the uterus-bladder interface (17.5%), myometrial thickness and hypoechoic retroplacental zone (25.6%), bladder line (22.6%), and previous caesarean sections (15.3%). The thresholds of scores for the prediction of accreta, increta, and percreta yielded 2.25-6.2, 6.2-8.95, and >= 8.95, respectively, with the positive and negative predictive value, and false positive rates of the scoring system were 96.68%, 95.44%, and 3.32%, respectively. Conclusions The scoring system can predict the severity of PAS in women with placenta previa. This will help identify the actual high-risk patients and improve their treatment.