Читать книгу Neonatal Haematology - Barbara J. Bain, Irene Roberts - Страница 17

The principal cytokine responsible for regulating erythropoiesis in the fetus and newborn, as in adults, is erythropoietin (EPO).³⁰ Since EPO does not cross the placenta, EPO‐mediated regulation of fetal erythropoiesis is predominantly under fetal control. The liver is the main site of EPO production in the fetus³¹ and the only stimulus to production under physiological conditions is hypoxia with or without anaemia (reviewed in reference 32). Little or no EPO is produced under normoxic conditions, but hypoxia very rapidly triggers expression by up to 200‐fold within 30 minutes, at least in hepatocyte cell lines.³³ This explains the high EPO levels in fetuses of mothers with diabetes mellitus or hypertension and in those with intrauterine growth restriction (IUGR) or cyanotic congenital heart disease;³⁴ EPO is also increased in fetal anaemia of any cause, including haemolytic disease of the fetus and newborn (HDFN). This, and the switch of EPO production from fetal liver to the neonatal kidney, may in part explain the physiological delay in triggering the production of new red blood cells, which is often not evident until the second month of life, even in healthy babies.