Cerebroplacental Ratio Prediction of Intrapartum Fetal Compromise according to the Interval to Delivery

A controversy exists about the accuracy of the cerebroplacental ratio (CPR) for the prediction of cesarean section for intrapartum fetal compromise (CS-IFC). Our aim was to evaluate whether the interval to delivery modifies the accuracy of CPR either as a single marker or combined with estimated fetal weight centile (EFWc), type of labor onset (TLO), and other clinical variables.

This was a multicenter retrospective study of 5,193 women with singleton pregnancies who underwent an ultrasound scan at 35+0-41+0 weeks and gave birth within 1 month of examination, at any of the participating hospitals in Spain, UK, and Italy. CS-IFC was diagnosed in case of an abnormal intrapartum fetal heart rate or intrapartum fetal scalp pH <7.20, requiring urgent cesarean section. The diagnostic ability of CPR in multiples of the median (CPR MoM) was evaluated at different intervals to delivery, alone and combined with EFWc, TLO, and other pregnancy data such as maternal age, maternal body mass index, parity, and fetal sex, for the prediction of CS-IFC by means of ROC curves and logistic regression analysis.

The predictive ability of CPR MoM for CS-IFC worsened with the interval to delivery. In general, the best prediction was obtained prior to labor and by adding information related to EFWc and TLO (AUC 0.71 [95% CI: 0.64-0.79], 0.73 [95% CI: 0.66-0.80], and 0.75 [95% CI: 0.69-0.81]; p < 0.0001). Addition of more clinical data did not improve prediction. In addition, results did not vary when only cases with spontaneous onset of labor were studied.

CPR MoM prediction of CS-IFC at the end of pregnancy worsens with the interval to delivery. Accordingly, it should be done in the short term and considering EFWc and TLO.