Abstract
The human uterus undergoes a marked reduction in length and weight in the first few weeks following birth. This was first described by Lyubetski, 1 and later, independently, by Bayer 2 and by Conte. 3 This reduction takes place through hypoplasia and hypotrophy of the uterine muscle, together with a disappearance of the marked natal hyperemia of the organ. It is supposed to be caused by the withdrawal at birth of a hormone produced by the placenta, the ovary or the tissues of both of these structures, (Aschner, 4 Herrmann, 5 Fellner, 6 , 7 Frank, 8 , 9 and others.) Little is known of the fetal growth of the uterus which precedes this natal reduction. The present study is based upon a total of 207 observations on the length of the uterus, 89 of fetal uteri, 62 of uteri of infants stillborn or dying within 48 hours after birth, and 56 uteri of children over 2 days and under 1 year of age.
A graphic analysis of this material is shown in the accompanying figure, in which the mean uterus length for 5 cm. intervals of total or crown-heel body-length, is plotted against the total body-length (as indicated on the base-line scale), and the computed age, (as indicated on the upper scale of the graph). Starting with an average length of about 2.5 mm. in the 5 to 10 cm. interval of crown-heel length, the viscus grows at a slow and fairly constant absolute rate, with respect to the total body-length, until approximately 7 lunar months (about 35 cm. crown-heel length). At this stage the average length of the uterus is approximately 17 mm.
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