Abstract
The course of the circulation, distribution of cardiac output and organ blood flow have been extensively studied in fetall lambs. No such information is available in human fetuses. 33 fetuses weighing 12–272 g (estimated gestation 10–20 weeks)were delivered by hysterotomy performed for legal abortion with the mother receiving general anesthesia and 50% O2. while placental circulation continued, a fire teflon canuula was inserted into the umbilical vein (UV), and nuclide-labeled microspheres were injected (within 3 min in most fetuses) to measure the distribution of blood flow. pH, PO2 and PCO2 were measured in arterialized maternal (MA) and in UV and feta arterial (FA) bloods. Mean values for MA were pH 7.47, PCO2 23, and PO2 183, for UV pH 7.41, PCO2 26, and PO2 60, and FA pH 7.27 PCO2 38 and PO2 34. Distribution of blood flow to each organ was expressed as a percentage of systemic venous return (%CO) in 4 weight groups <50g, 51-100, 101-150 and > 150 g. The % CO to placenta increased from a mean of 16.9 in <50 g to 33.1 in > 150 g fetuses; %CO to gut rose from 5.5 to 9.2 and to spleen from 0.4 to 0.9; %CO to kidneys fell from 6.5 to 3.2, myocardium 3.3 to 2.1, and brain 16.0 to 11.3. An average of 51.4% of UV blood passed through the ductus venosus; no significant change with growth was noted. In <50 g fetuses 50.7% of inferior vena caval blood crossed the foramen ovale to be distributed to the upper body, brain and myocardium; this fel to 32.3% in the > 150 g group. These studies demonstrate that the pattern of circulation in human fetuses is similar to that of other mammals, but there are quantitative differences in distribution of cardiac output. (Supported by NIH Grant HE 06285).
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Heymann, M., Rudolph, A., Teramo, K. et al. Circulation and its Distribution in Previable Human Fetuses. Pediatr Res 4, 443 (1970). https://doi.org/10.1203/00006450-197009000-00038
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DOI: https://doi.org/10.1203/00006450-197009000-00038