Two-dimensional phase-contrast MRI reveals changes in uterine arterial blood flow in pregnant women administered tadalafil for fetal growth restriction

Introduction: We aimed 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).

Methods: We recruited 14 pregnant women with FGR aged 20-44 years, at ≥20 weeks' gestation, between May 2019 and July 2020. They underwent 2D PC-MRI for UtA blood flow measurement 3 days (interquartile range: 2-4) after diagnosis. This group (FGR group) was compared with 14 gestational age (GA)-matched healthy pregnant women (control group). Six patients in the FGR group received treatment with tadalafil administered at 20 mg twice daily after the first MRI until delivery. They underwent a second MRI a week later.

Results: The median total UtA blood/body surface area was 420 mL/min/m² (290-494) in the FGR group and 547 mL/min/m² (433-681) in the control group (p = 0.01). Percent increase in blood flow were significantly different between the FGR cases treated with tadalafil and control at 15.8 % (14.3-21.3) and 4.2 % (3.6-8.7), respectively (p = 0.03).

Discussion: UtA blood flow in pregnant women with FGR was significantly lower than that in healthy pregnant women. Tadalafil is expected to improve UtA blood flow, thereby improving placental function in pregnant patients with FGR.