Hæmodynamic Factors in the Uterus during the Latter Part of Gestation

Abstract

ACCORDING to the data of Barcroft, Herkel and Hill¹, a critical change takes place in the rate of blood flow through the uterus of the rabbit after the twenty-second day of pregnancy. The rate of flow diminishes approximately one third between this and the twenty-fifth day, although it increases again by the twenty-seventh day of gestation. In an earlier paper by Barcroft and Rothschild², measurements were made of the volume of blood contained within the maternal vessels of the uterus on different days of pregnancy. The data of this study show that the volume of blood increases to a maximum by the twenty-eighth day and diminishes by fifty per cent during the next two days. The volume of the placental tissues during this time follows a parallel curve, so leading these investigators to the reasonable conclusion that the volume of blood in the uterus increases as the extent of the placental vascular bed increases. The cause of the changes in the rate of blood flow through these vessels has not, however, been described. When the foregoing data were used to estimate the efficiency of the uterine circulation during the latter part of gestation as certain growth changes take place, an insight was gained into some of the hæmodynamic factors operating at this time, providing a basis for interpreting the effects which Barcroft and his associates have reported.