Abstract

BACKGROUND: The accuracy of the cerebroplacental ratio (CPR) in predicting cesarean section for intrapartum fetal compromise (CS-IFC) prior to the onset of labor remains controversial. OBJECTIVES: To determine whether advancing gestational age (GA) in the final weeks of pregnancy enhances the predictive performance of CPR and other sonographic parameters for CS-IFC before labor. STUDY DESIGN: This multicentre retrospective study analysed 590 singleton pregnancies across four tertiary centres in Spain, Italy, and the UK. All participants underwent Doppler ultrasound assessment between 35+0 and 41+0 weeks of gestation and delivered within 24 hours of examination. CS-IFC was defined by abnormal intrapartum fetal heart rate patterns or fetal scalp pH <7.20 necessitating emergency caesarean delivery. The predictive performance of CPR, middle cerebral artery (MCA) pulsatility index (PI), and umbilical artery (UA) PI-expressed as multiples of the median (MoM)-was evaluated using ROC curve analysis and logistic regression, alone and in combination with estimated fetal weight centile (EFWc), fetal sex, and type of labour onset (TLO), stratified by gestational age. RESULTS: The highest overall predictive performance between 35 and 40 weeks of gestation was observed with the use of CPR MoM and MCA PI MoM (AUC 0.71, 95% confidence interval [95% CI], 0.64-0.79, P<.00001, AIC 343.6; AUC 0.70, 95% CI, 0.63-0.77, P<.00001, AIC 346.5, respectively). Predictive accuracy further improved with the inclusion of estimated fetal weight centile (EFWc) (AUC 0.73, CI 0.66-0.80, P<.00001, AIC 339.3; AUC 0.74, CI 0.68-0.80, P<.00001, AIC 336.4), and was enhanced even more when additional clinical variables, such as fetal sex and type of labor onset were incorporated (AUC 0.77, CI 0.71-0.83, P<.00001, AIC 327; AUC 0.78, CI 0.72-0.84, P<.00001, AIC 323.9).Across all models, predictive accuracy improved with advancing GA (P<.00001), peaking at 39 to 40 weeks. This trend was evident for cerebral Doppler indices (CPR MoM and MCA PI MoM), but not for UA PI or EFWc. The improvement in performance remained significant even when only fetuses appropriate for gestational age were analyzed. CONCLUSION: The predictive ability of cerebral Doppler for CS-IFC, in both high- and low-risk pregnancies, increases with advancing gestational age during the last weeks of gestation.