TY - CHAP M1 - Book, Section TI - Hematologic Disorders A1 - Wang, Michael A1 - McKinney, Christopher A1 - Nuss, Rachelle A1 - Ambruso, Daniel R. A2 - Hay Jr., William W. A2 - Levin, Myron J. A2 - Abzug, Mark J. A2 - Bunik, Maya PY - 2020 T2 - Current Diagnosis & Treatment: Pediatrics, 25e AB - The normal ranges for peripheral blood counts vary significantly with age. Normal neonates have a hematocrit of 45%–65%. The reticulocyte count at birth is relatively high at 2%–8%. Within the first few days of life, erythrocyte production decreases, and the values for hemoglobin and hematocrit fall to a nadir at about 6–8 weeks. During this period, known as physiologic anemia of infancy, normal infants have hemoglobin values as low as 10 g/dL and hematocrits as low as 30%. Thereafter, the normal values for hemoglobin and hematocrit gradually increase until adult values are reached after puberty. Premature infants can reach a nadir hemoglobin level of 7–8 g/dL at 8–10 weeks. Anemia is defined as a hemoglobin concentration two standard deviations below the mean for a normal population of the same gender and age. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/29 UR - accessmedicine.mhmedical.com/content.aspx?aid=1172110522 ER -