During first, 3-4 month of gestation erythrocytes are formed by
Stages of erythropoiesis according to development areIn the first 2 months of gestation - occurs in yolk sac (Mesoblastic phase)from 3rd month of gestation - In liver and spleen (Hepatic phase)From 20th week of gestation - In red bone marrow (myeloid phaseRef: Medical Physiology Indu Khurana 2015 edition, Page No:104
Yolk sac
Liver
Spleen
Bone marrow
Cardiovascular system