The Cardiac-Fetal-Placental Unit: links between umbilical venous flow and maternal hemodynamics in fetal growth restriction

Fetal growth restriction (FGR) is associated with significant perinatal morbidity and mortality, yet its identification remains challenging due to the limited sensitivity of conventional biometric assessment and the lack of a reliable tool for assessing placental function. Placental function depends on uteroplacental perfusion which, in turn reflects maternal cardiovascular adaptation to pregnancy. In this context, umbilical venous flow (UVF) has emerged as a quantitative parameter reflecting fetal blood supply and a potential surrogate marker of placental function. This narrative review aims to provide an overview of UVF and maternal hemodynamics, and to explore their interaction within the framework of the cardiac-fetal-placental unit. The current literature indicates that UVF is reduced in pregnancies complicated by FGR, and it correlates significantly with maternal cardiac output (CO) and systemic vascular resistance (SVR). A hypodynamic maternal profile (high SVR, low CO) is consistently associated with reduced UVF and impaired placental perfusion, regardless of fetal biometry. The integration of maternal cardiovascular assessment and UVF evaluation provides a functional perspective on placental insufficiency and may improve the identification of pregnancies at risk. Furthermore, this approach offers a potential framework for understanding the effects of maternal hemodynamic interventions on fetal growth.