Hematological and biochemical findings in fetal growth restriction and the relationship to hypoxia

Many factors influence the process of intrauterine growth so that some fetuses do not follow their growth potential. Intrauterine growth restriction (IUGR) is a complex disease with different severity depending on placental compromise. A specific “insufficient” placental phenotype has been described in IUGR, characterized by defects in placental metabolism and nutrient transport, particularly amino acids and lipids, but also micronutrients such as iron and folate. These changes are independent of severity and likely responsible for intrauterine programming. Less severe IUGR (with no compromise in umbilical blood flows and fetal heart rate) do not exhibit alterations in oxygen, lactate and glucose concentrations in fetal blood. IUGR fetuses become progressively hypoxic and lactacidemic with severity, showing placental impairment of mitochondria biogenesis and function, and defects in cell production of energy together with oxidative stress. These severe conditions have to be carefully balanced with the burden of prematurity in the timing of delivery.