Fetal ductal constriction is a potentially severe functional alteration, often causing right ventricular overload and insufficiency, tricuspid regurgitation and neonatal pulmonary hypertension. Classically, maternal administration of indomethacin and/or other nonsteroidal antiinflammatory drugs interfere in prostaglandin metabolism, leading to ductal constriction. However, many cases of fetal ductal constriction, as well as of persistent neonatal pulmonary artery hypertension, remain without an established etiology, being referred as “idiopathic”. In recent years, a growing body of evidences has shown that herbs, fruits, nuts, and a wide diversity of substances commonly used in daily diet, because of their high content of polyphenols, have definitive effects upon the metabolic pathway of inflammation, with consequent inhibition of prostaglandins synthesis. This anti-inflammatory action of polyphenols, when ingested during the third trimester of pregnancy, may interfere with the dynamics of fetal ductus arteriosus flow and cause ductal constriction. This review has the purpose to approach these new evidences, which may influence dietary orientation during pregnancy.