The Influence of Hyperoxygenation on Fetal Brain Vascularity Measured Using 3D Power Doppler Ultrasound and the Index “Fractional Moving Blood Volume”

Abstract

<b><i>Introduction:</i></b> Maternal hyperoxygenation effects on fetal cerebral hemodynamics are largely unknown. This study aimed to determine efficacy and reliability of a validated power Doppler ultrasound (US) index, fractional moving blood volume (FMBV), at measuring fetal cerebral vasculature changes during maternal hyperoxia. <b><i>Methods:</i></b> The fetal cerebral effects of 10 min of hyperoxygenation at 2 flow rates (52%/60% FiO₂) were evaluated in women in their third trimester of pregnancy. 2D-US and 3D-US in a transverse plane were performed before, during, and following maternal hyperoxygenation with FMBV estimation performed offline. <b><i>Results:</i></b> Forty-five cases provided data for analysis. Mean intraobserver ICCs were 0.89 (3D-FMBV) and 0.84 (2D-FMBV). A significant difference in vascularity before and during and before and after 60% hyperoxia was observed (<i>p</i> &#x3c; 0.05), whereas no significant differences were found at 52% hyperoxia (<i>p</i> &#x3e; 0.05). Significant differences in vascularity were found between 2D-FMBV and 3D-FMBV (<i>p</i> &#x3c; 0.01). <b><i>Conclusion:</i></b> Measurement of fetal cerebral vascularity by 3D-FMBV and 2D-FMBV was highly reproducible. The differing cerebral vascular changes seen with 60% but not 52% FiO₂ suggest a possible “threshold effect” that may have influenced prior studies. Further studies are needed to assess cerebral effects of maternal hyperoxygenation on compromised fetuses.