The vertebroplacental ratio as an alternative to the cerebroplacental ratio in the evaluation of the fetus at the end of pregnancy

Abstract

Objective: Low cerebroplacental ratio (CPR) near term has emerged as a marker of fetal adverse outcome. The aim of this study was to evaluate the predictive accuracy of an alternative ratio using the vertebral artery (VA) (vertebroplacental ratio or VPR) for acid–base status at birth.

Methods: This was a prospective cohort study of 1470 pregnancies undergoing an ultrasound assessment of the umbilical artery, middle cerebral artery and VA Doppler beyond 34 weeks’ gestation within 14 days of delivery. The CPR multiples of the median (MoM) and VPR MoM were calculated to adjust for gestational age. The relationship between the fetal Dopplers and the umbilical cord pH (arterial and venous) was evaluated statistically, and depicted graphically using three-dimensional (3D) trend surfaces, 2D contour graphs and ROC curves.

Results: All the studied parameters were poorly associated with neonatal acid–base status, although this association was slightly better for venous pH. The importance of BW centile was smaller than that of CPR and VPR MoM, however, both hemodynamic parameters were similarly associated with neonatal pH.

Conclusions: Concerning fetal surveillance near term, the importance of cerebroplacental hemodynamics surpasses that of BW. Furthermore, in the evaluation of fetal wellbeing VPR behaves as a valid alternative to CPR.

Keywords:

• Cerebroplacental ratio
• fetal Doppler
• fetal growth restriction
• vertebroplacental ratio

Disclosure statement

The authors report no conflicts of interest.