Postpartum uterine artery Pulsatility Index as a predictor of retained products of conception – A prospective blinded study

OBJECTIVE: Postpartum retained products of conception (RPOC) are a major health concern. The aim of our study was to assess whether a single postpartum measurement of uterine artery blood flow can predict postpartum RPOC. METHODS: As part of our routine practice, parturients considered at risk for RPOC underwent a series of sequential ultrasounds followed by hysteroscopy if needed. In this study, we measured uterine artery Pulsatility Index (PI) bilaterally at day 1-3 postpartum. Both the patients and the clinical team were blinded to the Doppler measurements. Cases in which RPOC was identified in hysteroscopy were compared with cases in which RPOC was ruled out. RESULTS: Minimal uterine PI was strongly associated with RPOC (median PI 0.78 [interquartile range 0.69-0.85] vs. 1.19 [interquartile range 0.88-1.4], P = 0.004). Receiver operating characteristic analysis demonstrated an area under the curve of 0.837 (95% confidence interval 0.731-0.942). Minimal uterine artery PI was the best predictor of RPOC. A uterine PI value <0.95 had a sensitivity of 100% and specificity of 68.3% in predicting RPOC. CONCLUSIONS: Low uterine artery PI, when measured in the first days after delivery, is the best single-parameter predictor of RPOC.