Anemia and polycythemia in the newborn.

1. Erica Hyman Kates, MD 1. Children’s Hospital at Montefiore Bronx, NY 1. Jacqueline S. Kates, MD 1. Long Island Jewish Medical Center New Hyde Park, NY Physiologic Anemia of Infancy. Glader B. In: Behrman RE, Kliegman RM, Jenson HB, eds. Nelson’s Textbook of Pediatrics. 17th ed. Philadelphia, Pa: WB Saunders Co; 2004:1610– 1611 Anemia in Children. Irwin JJ, Kirchner JT. Am Fam Physician. 2001;64 :1379– 1386[OpenUrl][1][PubMed][2] Differential Diagnosis and Management of Anemia in the Newborn. Bizzarro MJ, Colson E, Ehrenkranz RA. Pediatr Clin North Am. 2004;51 :1087– 1107[OpenUrl][3][CrossRef][4][PubMed][5] Neonatal Polycythemia. Garcia-Prats JA. UpToDate. Available at: www.uptodate.com Red blood cell (RBC) mass in the newborn is highly variable. As an infant makes the transition from the intrauterine to the extrauterine environment, a change occurs in both the mass and the composition of RBCs. The range of normal, while clearly defined, is wide because of the many fluctuating variables involved in the physiology of the peripartum period. In utero, fetal hemoglobin predominates. When compared with adult hemoglobin, fetal hemoglobin has enhanced oxygen-binding capacity, a characteristic that allows sufficient oxygen transfer to the fetus in the absence of gas exchange with the external environment. Even with fetal hemoglobin’s increased affinity for oxygen, the intrauterine environment is relatively hypoxic. As a result, the hemoglobin level in a near-term fetus or term infant is relatively high. The normal hemoglobin concentration for a term newborn is 19.3±2.2 g/dL (193±220 g/L), with a hematocrit of 61%±7.4% (0.61±0.074), values that continue to rise until they reach a maximum at about 2 hours after birth. Within the first week after delivery, hemoglobin and hematocrit values begin to drop in response to the higher ambient oxygen concentration ex utero. It is postulated that this increase in oxygen concentration, combined with a rising percentage of adult hemoglobin, … [1]: {openurl}?query=rft.jtitle%253DAmerican%2Bfamily%2Bphysician%26rft.stitle%253DAm%2BFam%2BPhysician%26rft.aulast%253DIrwin%26rft.auinit1%253DJ.%2BJ.%26rft.volume%253D64%26rft.issue%253D8%26rft.spage%253D1379%26rft.epage%253D1386%26rft.atitle%253DAnemia%2Bin%2Bchildren.%26rft_id%253Dinfo%253Apmid%252F11681780%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [2]: /lookup/external-ref?access_num=11681780&link_type=MED&atom=%2Fpedsinreview%2F28%2F1%2F33.atom [3]: {openurl}?query=rft.jtitle%253DPediatric%2Bclinics%2Bof%2BNorth%2BAmerica%26rft.stitle%253DPediatr%2BClin%2BNorth%2BAm%26rft.aulast%253DBizzarro%26rft.auinit1%253DM.%2BJ.%26rft.volume%253D51%26rft.issue%253D4%26rft.spage%253D1087%26rft.epage%253D107%252C%2Bxi%26rft.atitle%253DDifferential%2Bdiagnosis%2Band%2Bmanagement%2Bof%2Banemia%2Bin%2Bthe%2Bnewborn.%26rft_id%253Dinfo%253Adoi%252F10.1016%252Fj.pcl.2004.03.006%26rft_id%253Dinfo%253Apmid%252F15275990%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [4]: /lookup/external-ref?access_num=10.1016/j.pcl.2004.03.006&link_type=DOI [5]: /lookup/external-ref?access_num=15275990&link_type=MED&atom=%2Fpedsinreview%2F28%2F1%2F33.atom