Two-dimensional phase-contrast magnetic resonance imaging reveals changes in uterine arterial blood flow in pregnant women treated with tadalafil for fetal growth restriction: A prospective study.

Objective: To examine the effect of uterine arterial (UtA) blood flow changes after tadalafil treatment for fetal growth restriction (FGR) using two-dimensional (2D) phase-contrast magnetic resonance imaging (PC-MRI). Design: Prospective, controlled study. Setting: Single tertiary center. Population or Sample: Fourteen pregnant women with FGR aged 20–44 years and at ≥20 weeks’ gestation were recruited between May 2019 and July 2020. Methods: They underwent 2D PC-MRI for UtA blood flow measurement 3 days after diagnosis. They were compared with 14 gestational age (GA)-matched healthy pregnant women (control group). Six patients in the FGR group received tadalafil at 20 mg twice daily after the first MRI until delivery. They underwent a second MRI 1 week later and were compared with 6 of the 14 GA-matched healthy pregnant women. Main Outcome Measures: Total UtA blood/body surface area Results: The median total UtA blood/body surface area was 420 mL/min/m (290–494) in the FGR group and 547 mL/min/m (433–681) in the control group (p=0.01). Percent increases of blood flow in the FGR and control groups were significantly different at 68.8% (51–75) and 18.8% (16–57), respectively (p<0.01). Both intraobserver reproducibility (r=0.997, p<0.01; intraclass correlation coefficients (ICC), 0.997) and interobserver reproducibility (r=0.997, p<0.01; ICC, 0.998) were high. Conclusions: UtA blood flow in pregnant women with FGR was significantly lower than that in healthy pregnant women. Tadalafil may improve UtA blood flow, thereby improving placental function in pregnant patients with FGR.