Association of third trimester cerebroplacental ratio with obstetric and neonatal outcomes in uncomplicated singleton pregnancies: a prospective observational study

Abstract

Background: The cerebroplacental ratio (CPR) integrates information from the middle cerebral and umbilical artery circulations and may reflect fetal haemodynamic adaptation. This study evaluated the association between third-trimester CPR and obstetric and neonatal outcomes in uncomplicated singleton pregnancies. Methods:  This prospective observational study included 90 uncomplicated singleton pregnancies in the third trimester. Middle cerebral artery pulsatility index and umbilical artery pulsatility index were assessed by colour Doppler, and CPR was calculated as MCA PI/UA PI. The last CPR measurement before delivery was used for analysis. CPR values were compared between pregnancies with and without selected obstetric and neonatal outcomes. A secondary analysis used the study-derived CPR cut-off of ≤0.85. Results: Mean CPR was significantly lower with non-reactive NST than reactive NST (0.72±0.19 vs 1.05±0.20; p=0.001). Lower CPR was also associated with Apgar score <7 at 5 minutes, NICU admission, meconium-stained liquor, respiratory distress syndrome, neonatal death, sepsis, assisted and extensive respiratory support, and birth weight <10th centile (p≤0.002). CPR was lower among cesarean than vaginal deliveries (0.81±0.22 vs 1.03±0.20; p=0.002). Overall, 72 (80.0%) had an adverse perinatal outcome; 52/54 (96.3%) with CPR ≤0.85 had an adverse outcome versus 20/36 (55.6%) with CPR >0.85 (p<0.001). Conclusions: Lower third-trimester CPR was associated with several adverse obstetric and neonatal outcomes. The study-derived cut-off of ≤0.85 was also associated with adverse perinatal outcome. CPR may provide adjunctive information for perinatal risk assessment, while the study-derived threshold requires external validation.