This study tested the hypothesis that restricting a pregnant woman's intake of polyphenol-rich foods for at least two weeks improves ductus arteriosus blood flow dynamics in healthy third-trimester fetuses, as was previously shown in fetuses with ductal constriction. 46 pregnant women restricted their polyphenol intake from an average of 1277 mg/day to 126 mg/day. Their fetuses showed significant decreases in ductal velocities and RV/LV ratio, and an increase in ductal pulsatility index. A control group of 26 women showed no significant changes. The study suggests that reducing maternal polyphenol intake improves fetal ductal hemodynamics in normal pregnancies.