Abnormally pulsatile umbilical artery (UA) Doppler ultrasound velocity waveforms are a hallmark of severe or early-onset placental-mediated intrauterine growth restriction (IUGR) while milder late-onset IUGR pregnancies typically have normal UA pulsatility. The diagnostic utility of these waveforms to detect placental pathology is thus limited, and hampered by factors outside of the placental circulation including fetal cardiac output. We developed a new ultrasound approach to isolate that portion of the UA Doppler waveform that originates from the placenta, specifically the reflected pulse pressure wave propagating backward along the UA. Ultrasound measurements of UA lumen diameter and flow waveforms were used to decompose the observed flow waveform into its forward and reflected components. Evaluation of CD1 and C57BL/6 mice at E15.5 and E17.5 demonstrated that the reflected waveforms diverged between the strains at E17.5, mirroring known changes in the fractal geometry of the feto-placental arteries at these ages. These experiments demonstrate the feasibility of non-invasively measuring wave reflections that originate from the feto-placental circulation. The observed reflections were consistent with theoretical predictions based on the area ratio of parent to daughters at bifurcations in the feto-placental arteries suggesting that this approach could be used in the diagnosis of feto-placental vascular pathology that is prevalent in human IUGR. Given that the proposed measurements represent a subset of those currently used in human fetal surveillance, the adaptation of this technology could extend the diagnostic utility of Doppler ultrasound in the detection of placental vascular pathologies that cause IUGR.
- intrauterine growth restriction
- umbilical artery
- wave reflection
- Copyright © 2016, American Journal of Physiology-Heart and Circulatory Physiology