# Optimizing Cerebroplacental Ratio Thresholds: Superiority of ≤1.1 Over Less Than 1 for Predicting Adverse Perinatal Outcomes

## TL;DR

A study finds that using a cerebroplacental ratio threshold of ≤1.1 is better than <1 for predicting poor outcomes in late-term pregnancies.

## Contribution

The study demonstrates that a CPR threshold of ≤1.1 is more effective than the traditional <1 threshold in predicting adverse perinatal outcomes.

## Key findings

- CPR ≤1.1 showed stronger associations with abnormal fetal heart rate, meconium-stained liquor, and NICU admissions.
- Using CPR ≤1.1 improved predictive accuracy for operative deliveries and emergency caesarean due to fetal distress.
- The threshold ≤1.1 detected more at-risk pregnancies compared to the conventional CPR <1 cut-off.

## Abstract

Background

The cerebroplacental ratio (CPR), calculated as the ratio of middle cerebral artery pulsatility index to umbilical artery pulsatility index, is a non-invasive Doppler marker reflecting placental function and fetal adaptation. While a CPR cut-off <1 has been traditionally used, emerging evidence suggests that ≤1.1 may provide superior predictive accuracy for adverse perinatal outcomes.

Objective

This study aimed to compare the predictive value of CPR cut-offs <1 and ≤1.1 in identifying term pregnancies at risk of intrapartum complications and adverse neonatal outcomes.

Methods

This prospective observational study was conducted at Maharishi Markandeshwar Medical College and Hospital, Kumarhatti, India, over 18 months, including 180 antenatal women with uncomplicated singleton pregnancies at 37-42 weeks. Doppler ultrasonography was performed to assess CPR, and outcomes were analyzed against the two cut-off values. Primary outcomes were intrapartum fetal heart rate abnormalities, mode of delivery, liquor characteristics, birth weight, and neonatal intensive care unit (NICU) admission.

Results

CPR <1 was significantly associated with abnormal fetal heart rate (100% vs. 18.6%; p=0.001), operative deliveries (100% vs. 20.3%; p=0.009), and NICU admissions (100% vs. 19.8%; p=0.001). When the threshold was raised to ≤1.1, predictive strength improved, with abnormal cardiotocography (CTG) (73.5% vs. 7.5%; p=0.001), higher emergency caesarean for fetal distress (100% vs. 84.6%; p=0.043), meconium-stained liquor (41.2% vs. 1.4%; p=0.001), and NICU admission (64.7% vs. 11%; p=0.001) all showing stronger associations.

Conclusion

CPR ≤1.1 outperforms the conventional cut-off of <1 in predicting adverse perinatal outcomes at term. Incorporating this threshold into routine antenatal surveillance may allow the earlier identification of at-risk fetuses and timely intervention to improve neonatal outcomes.