Cerebral-Placental-Uterine Ratio in the Early Third Trimester as a Predictor of Small-for-Gestational-Age Birthweight: A Prospective Cohort Study.

OBJECTIVES

The diagnosis of late-onset fetal growth restriction is challenging, with a low detection rate using ultrasonographic estimation of fetal weight and subtle Doppler changes in commonly assessed fetal vessels. The cerebral-placental-uterine ratio (CPUR) has been reported to better predict small-for-gestational-age (SGA) birthweight. However, its use in the early third trimester has never been evaluated. This study aimed to evaluate the role of the CPUR in the early third trimester for predicting SGA at birth.

METHODS

This prospective cohort study included 228 women at 28-31 weeks gestation with appropriate-for-gestational-age (AGA) fetuses between May and December 2023 in a tertiary-level hospital. The umbilical, middle cerebral, and uterine artery pulsatility indexes (PIs) were measured to calculate the cerebroplacental ratio and CPUR (CPR-PI/UtA-PI). Parameters were compared between women with AGA and SGA newborns. After determining the CPUR cutoff point, predictors of SGA birthweight were identified using logistic regression analysis.

RESULTS

Fifty-one women (22.4%) delivered SGA infants. The optimal CPUR cutoff point for predicting SGA birthweight was 2.1 (sensitivity 88.7%, specificity 31.4%). The SGA group had significantly lower estimated fetal weight, estimated fetal weight percentile, abdominal circumference (AC), AC percentile, and cerebroplacental ratio, than the AGA group. A low CPUR was significantly more common in the SGA than in the AGA group (31.4% vs. 11.3%, P = 0.001). After multivariate analysis, a low CPUR (<2.1) was significantly associated with SGA at birth (odds ratio 4.39; 95% CI 1.88-10.44, P < 0.001).

CONCLUSIONS

Early third-trimester CPUR was an independent predictor of SGA at birth.