A Pilot Study of Ultrasound Assessment of Umbilical Cord and Placental Vascular Flow for Cord Accident Stillbirth Prevention.

Abstract

Our objective was to determine the feasibility and interobserver reliability of umbilical cord and placental arteriolar flow assessment in low-risk pregnancies near term. This was a prospective pilot study in low-risk pregnancies at 36 weeks with anterior placentas. We excluded any with an indication for antenatal testing or delivery before 39 weeks. Each participant underwent two ultrasounds by different examiners, which included arterial and venous velocimetry at three cord sites (fetal, free loop, and placental) in addition to maternal and fetal placental arterioles. The interobserver reliability was quantified using the Pearson correlation coefficient with that of standard clinical parameters serving as a benchmark for interpretation. Among 53 participants scanned at 356/7-371/7 weeks, the mean examination duration was 20.5 ± 4.2 minutes. Ascertainment success was high for measures at the free loop, placental cord insertion, and fetal placental arterioles (range 90.6%-99.1%) and was lower at the fetal cord insertion and maternal spiral arterioles (range 47.2%-87.7%). Interobserver reliability estimates for free-loop systolic/diastolic and pulsatility index ranged from 0.38 to 0.44. Interobserver reliability for experimental parameters varied by measurement site, and all were poor at the fetal insertion and in placental arterioles. Parameters had significant variation across cord sites (range 4.3%-21.7%). In our cohort, flow assessments of the free loop, placental insertion, and placental arterioles are feasible, but interrater reliability varies by measurement type and cord site. Future studies are needed to establish feasibility and reliability in nonanterior placentation and to assess clinical relevance.