These notes covers briefly later Postnatal Heart Development, not the changes that occur in the neonate following birth (see Birth Cardiovascular Changes). There have been several studies that have looked not only at absolute heart growth, as measured by weight, but also the comparitive contribution (%) of total body mass between different species. During the first postnatal year the heart increase weight at has its greatest rate.
The volume of the heart ventricles at birth are approximately the same.
The data for heart growth (weight) below is from a historic article by Smith (1928) reviewed recently in Birth defects (2003).
|Age (years)||Male (grams)||Female (grams)|
|Birth to 1 year||45||35|
Weight values are averages and there is great variability in each measurement.
(data from: Smith HL. 1928. The relation of the weight of the heart to the weight of the body and of the weight of the heart to age. Am Heart J 4: 79–93.; reviewed also in KW Hew and KA Keller, Postnatal Anatomical and Functional Development of the Heart: A Species Comparison, Birth Defects Research (Part B) 68:309-320, 2003)
Cardiac muscle cells, myocytes, in the newborn heart are mainly mononucleated and number about half the total adult number.