abnormal extraembryonic tissue morphology abnormal blood cell morphology/development abnormal embryonic hematopoiesis MP:0003396 MPheno.ontology abnormal primitive hematopoiesis anomaly in the development of primarily large, nucleated erythroblasts as well as some megakaryocytes and primitive macrophages that circulate in the embryonic and extraembryonic tissues, and which occurs in blood islands in the yolk sac from E7-E11 in the mouse and through 10 weeks in humans