Idiopathic fetal growth restriction: a pathophysiologic approach.

Known causes of fetal growth restriction (FGR) can be traced in up to 40 percent of the cases. In the remainder of cases, FGR is idiopathic in origin. Evidence from experimental studies, antenatal findings at Doppler velocimetry of the uterine and umbilical arteries, and placental pathology studies suggests that idiopathic FGR can be divided into three groups: 1) primary abnormality in the uteroplacental perfusion; 2) primary abnormality in the fetoplacental perfusion; and 3) abnormal villous structure at the interface between fetal and maternal circulation. An improved understanding of the pathophysiology of idiopathic FGR is crucial to gain insight into its pathogenesis.