<prompt> Up to 6 weeks of gestation erythropoiesis occurs in?Yolk sacBone marrowSpleenLiver  <response>: ANSWER: A Yolk sacREF: Guyton, 6th edition, page 420, Wintrobe s clinical hematology 12th ed page 90, Williams hematology 8th ed chapter 6See details of fetal erythropoiesis in Physiology December 2011 