Erythropoietin (EPO) is a glycoprotein hormone with a molecular weight of 30.4 kDa, responsible for regulating erythropoiesis in adults, newborns and fetuses. During pregnancy, the concentration of maternal serum EPO increases linearly to allow for effective erythropoiesis over time. In the fetus, in the first 30 weeks of gestation, the liver is the main synthetic organ. Thereafter, there is a progressive transfer of the synthesis of EPO to the kidneys. In the long term, under normal conditions of oxygenation, the fetal synthesis of EPO is mainly ensured by the kidney.

Because of the impossibility of making EPO tissue reserves and the inability of EPO to pass the placental barrier, the concentration of circulating EPO in the fetus reflects the balance between production and elimination. During the last trimester of pregnancy, in the absence of patent hypoxia, fetal concentrations of circulating EPO are between 10 and 50 mIU /ml, while in amniotic fluid the EPO is found at lower concentrations, between 2 and 20 mIU /ml.

In adults, EPO synthesis is primarily renal, and incidentally hepatic, even if in certain pathological situations (end-stage kidney disease or polycystosis) the liver is able to take over and synthesize EPO with an electrophoretic profile similar to that of the EPO from the umbilical cord, but often in insufficient quantities.

The objective of this study is to describe the forms of EPO in newborns and to compare possible iso-forms with those of adults.

Inclusion Criteria:

• infant or child under 1 year old hospitalized or consulting at CHU Dijon Bourgogne whose parents have not opposed participation in the study

Exclusion Criteria:

• child treated with recombinant erythropoietin

newborn or child under 1 year of age