The importance of the cerebro-placental ratio at term for predicting adverse perinatal outcomes in appropriate for gestational age fetuses.

Objectives: This study investigates the relationship between the cerebro-placental ratio (CPR) measured at 40+0 weeks' gestation and perinatal outcomes to determine a CPR cut-off that may justify induction of labor at term in appropriately grown fetuses (AGA). Although CPR is used for monitoring growth-restricted fetuses, its role in guiding labor induction decisions for AGA pregnancies at term remains unclear.

Methods: A retrospective cohort study was conducted using data from 491 singleton pregnancies with intended vaginal deliveries between 2015 and 2021. CPR was assessed at the actual estimated date of delivery (40+0 weeks' gestation). Adverse pregnancy outcome (APO) as the primary endpoint was defined by admission to neonatal intensive care unit (NICU), umbilical cord blood pH<7.1, 5-min APGAR<7 or interventions-due-to-fetal-distress during labor (IDFD=vaginal-operative delivery or emergency caesarean section).

Results: APO nearly doubled (adjOR 1.7; CI 1.007-2.905) when CPR was below our calculated cut-off of 1.269 (18.4 vs. 32.3 %, p=0.002) and NICU admissions (4.8 vs. 11.1 %, p=0.020) and IDFD (12.5 vs. 21.2 %, p=0.027) significantly increased. The positive predictive value for the presence of APO using our cut-off was 32.4 %, and the negative predictive value 81.6 %.

Conclusions: Our data confirm a predictive value of a reduced CPR at term with impaired perinatal outcome. The cut-off of CPR<1.269 may guide decision-making regarding induction of labor. Further prospective studies are needed to confirm these findings.