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NeoReviews Vol.7 No.11 2006 e564
© 2006 American Academy of Pediatrics

Commentary

The Benefits of Cord Blood Collection

The first 300 words of the full text of this article appear below.

In this issue of NeoReviews, Dr Diaz-Rossello offers an interesting international perspective on the timing of cord clamping for stem cell donation. To extend the discussion of this issue, this commentary reviews the biology of early hematopoiesis and neonatal anemia, the current literature on cord blood, and cord blood collection procedures.

Fetal hematopoiesis begins at 2 weeks of human embryogenesis and originates from mesenchymal cells in the yolk sac. This process overlaps at 6 weeks with liver hematopoiesis in migrated pluripotent stem cells from the yolk sac. By 10 weeks, yolk sac hematopoiesis (mostly erythropoiesis) becomes undetectable, and the liver becomes the major site of blood formation during mid-gestation. Finally, at 20 weeks, medullary hematopoiesis begins with migration of pluripotent stem cells from the liver to the bone marrow. During this phase of blood formation, granulocyte and megakaryocyte production becomes significant. Liver hematopoiesis begins to slow, stopping completely right before birth. (1) Although studied in a variety of animal and laboratory models, we still do not fully understand the triggers for changes in fetal hematopoiesis. (2) Many believe it involves changes in the hematopoietic microenvironment and the interaction of various cytokines. (3)

Following delivery, hematopoiesis shifts completely to medullary sites, including the vertebrae, ribs, sternum, pelvis, scapulae, skull, and extremities. After childhood, blood formation gradually shifts to the extremities (proximal humerus and femur), with continued hematopoiesis in the axial marrow sites. Different congenital or acquired hematologic diseases may reactivate earlier sites of blood formation.

Human infants are born plethoric, ie, with an abundance of red blood cells. Immediately at birth, the neonatal blood volume is between 80 and 95 mL/kg, depending on the time of cord clamping. Within 4 hours, volume contracts as much as 25%. At term birth, the normal hemoglobin (Hgb) ranges . . . [Full Text of this Article]

Joshua D. Schiffman, MD

Division of Pediatric Hematology/Oncology
Department of Pediatrics
Lucile Packard Children’s Hospital
Stanford University
Palo Alto, Calif






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Copyright © 2006 by the American Academy of Pediatrics.