Comparison of three Doppler ratio indices for predicting adverse perinatal outcomes in late-onset fetal growth restriction.

OBJECTIVE

To compare the predictive performance of three Doppler ratio indices-cerebroplacental ratio (CPR), cerebral-placental-uterine ratio (CPUR), and uteroplacental-cerebral ratio (UCPR)-for adverse perinatal outcomes in late-onset fetal growth restriction (FGR).

METHODS

This retrospective cohort study analyzed singleton pregnancies diagnosed with late-onset FGR (≥32 weeks) between October 2024 and January 2026. Doppler parameters-umbilical artery pulsatility index (UA-PI), middle cerebral artery pulsatility index (MCA-PI), and mean uterine artery pulsatility index (mean UtA-PI)-were retrieved at diagnosis. Three indices were calculated: CPR (MCA-PI/UA-PI), CPUR (CPR/mean UtA-PI), and UCPR ((UA-PI + mean UtA-PI)/MCA-PI). Univariable and multivariable logistic regression models (adjusting for estimated fetal weight percentile and gestational age) were constructed. Internal validation used bootstrap resampling (n = 1000). AUC pairwise comparisons employed the DeLong test, and decision curve analysis (DCA) evaluated clinical utility.

RESULTS

Of 155 pregnancies, adverse perinatal outcomes occurred in 48 (31.0%). Affected pregnancies had earlier delivery (35.88 ± 1.17 vs. 37.74 ± 1.20 weeks, p < 0.001) and lower birth weight (1948.04 ± 213.15 vs. 2336.05 ± 306.45 g, p < 0.001). All indices differed significantly between groups (p < 0.05). In univariable analysis, CPUR achieved the highest AUC of 0.781 (95% CI: 0.698-0.856), followed by UCPR (0.777, 95% CI: 0.698-0.851) and CPR (0.740, 95% CI: 0.652-0.820). Optimal cutoffs were CPR ≤ 1.44, CPUR ≤ 1.38, and UCPR > 1.32. Pairwise comparisons revealed no statistically significant differences (all p > 0.05). In multivariable analysis, all ratios remained independently associated with adverse outcomes (CPR: aOR 0.37; CPUR: aOR 0.29; UCPR: aOR 2.71; all p < 0.001), with improved discrimination (AUC: 0.793-0.816). DCA demonstrated clinical benefit across threshold probabilities of 15-50%.

CONCLUSIONS

In late-onset FGR, CPR, CPUR, and UCPR showed comparable predictive accuracy for adverse perinatal outcomes, each maintaining independent predictive value after adjustment for disease severity and gestational age. Statistically non-significant pairwise differences should not be interpreted as clinical equivalence; multicenter prospective studies are warranted. These indices may assist clinical decision-making in late-onset FGR management.