Vertebroplacental ratio for prediction of perinatal outcome and operative delivery for suspected fetal compromise: prospective observational cohort study
Authors: Packet B. , Van Severen R. , Richter J. 
Published: February 2025

Objective

To investigate differences in fetal vertebroplacental ratio (VPR) depending on the occurrence of operative delivery for suspected fetal compromise (ODFC) and composite perinatal outcome (CPO) at delivery.

Methods

This was a prospective observational cohort study conducted in the Department of Obstetrics and Gynecology at the University Hospitals of Leuven, Leuven, Belgium, between December 2022 and April 2024. Women with a term (37–42 gestational weeks) singleton pregnancy with an appropriate‐for‐gestational‐age (AGA) fetus were recruited, before cervical dilatation reached 5 cm, for sonographic fetal weight estimation (EFW) and Doppler sonography of the umbilical artery (UA), umbilical vein (UV), middle cerebral artery (MCA) and vertebral artery (VA). The primary outcomes were differences in VPR multiples of the median (MoM) depending on the occurrence of ODFC and CPO at delivery (based on UA cord blood pH and base excess, 1‐min and 5‐min Apgar score, and neonatal intensive care unit admission). We explored the technical feasibility of fetal Doppler sonography in this setting and differences in Doppler findings from individual fetal vessels (UA, UV blood flow (UVF), MCA, VA) and related parameters (UVF/EFW and cerebroplacental ratio (CPR)). We also investigated whether adding individual sonographic variables to baseline clinical prediction models could improve discriminatory power (using the area under the receiver‐operating‐characteristics curve (AUC)) and predictive accuracy (using the Brier score) for both outcomes.

Results

A total of 161 women were recruited. The mean ± SD maternal age was 32.2 ± 3.8 years and approximately half (53.4%) of the women were nulliparous. Most (88.2%) women had labor induced. The mean ± SD gestational age at delivery was 39.3 ± 1.0 weeks and the mean ± SD ultrasound‐to‐delivery interval was 10.4 ± 2.75 h. An adverse CPO occurred in 13.3% of cases and ODFC occurred in 17.4%. No difference in mean VPR MoM was observed between cases with normal vs adverse CPO (1.04 ± 0.26 vs 1.17 ± 0.25; P = 0.09), or between cases which underwent ODFC vs those which did not (1.06 ± 0.29 vs 1.06 ± 0.26; P = 0.97). Likewise, no differences in other Doppler variables (UA pulsatility index (PI) MoM, MCA‐PI MoM, VA‐PI MoM, CPR MoM) were observed for both outcomes, except for significantly higher UVF rates in the adverse CPO group (both absolute (P = 0.02) and corrected for EFW (P = 0.048)). For both outcomes, adding VPR MoM or any other sonographic variable to baseline prediction models, which consisted solely of clinical variables, did not improve predictive accuracy or discriminatory power. The baseline model AUC and Brier score values were 0.68 (95% CI, 0.57–0.79) and 0.14 for adverse CPO, and 0.72 (95% CI, 0.61–0.83) and 0.13 for ODFC, respectively.

Conclusions

Although technically feasible to measure in most women with an AGA fetus admitted for spontaneous or induced labor at term, no difference in VPR MoM was observed depending on the occurrence of ODFC or CPO at delivery. Moreover, adding VPR MoM or any other sonographic variable to a baseline clinical prediction model did not improve predictive accuracy or discriminatory power for either outcome. Hence, peripartum ultrasound for the assessment of fetal weight and placental function has limited added value for predicting adverse labor outcomes in a low‐risk obstetric population. © 2025 International Society of Ultrasound in Obstetrics and Gynecology.