This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables.
In Reply.—Dr Fikar quite correctly notes that the reticulocytosis observed in almost all newborns accounts for some of the macrocytosis at this age. Usually by 5 days of life, however, both term and preterm infants will experience a decline in reticulocyte count to a level the same as or lower than that in older infants and children. Thus, the continued decline in MCV cannot solely be a reflection of changes in reticulocyte count. Active erythropoiesis generally ceases until 6 to 12 weeks of age in term infants and until 4 to 8 weeks of age in preterm infants. Even on resumption of active erythropoiesis, extremely tiny babies (who really ought still to be in utero) do not seem to experience a rise in MCV as they begin to produce new RBCs. This is an enigma that defies explanation.
STOCKMAN JA. Mean Corpuscular Volume-Reply. Am J Dis Child. 1981;135(8):770. doi:10.1001/archpedi.1981.02130320078029
Customize your JAMA Network experience by selecting one or more topics from the list below.
Create a personal account or sign in to: