Maternal progesterone and fetal cortisol responses to hypoxemia in pregnant sheep

Li-Hua Wu
The placenta is an important endocrine organ producing large amounts of steroid and protein hormones which are released into the maternal and fetal circulations. Moreover, it has a very high metabolic rate and consumes a significant proportion of the oxygen and glucose delivered to the uterus and its contents. However, while there have been many studies on the effects of hypoxemia on fetal cardiovascular, metabolic and endocrine functions, there are limited data on the effects of reduced
more » ... s of reduced oxygenation on placental endocrine activities. In the present study, we examined the effects of acute (2-h) moderate (maternal Pao₂ lowered by 27-35%, n=5) and severe (maternal Pao₂ lowered by 41-58%, n=4) hypoxemia on placental progesterone output into the maternal circulation in 7 chronically instrumented pregnant sheep (125 to 136 d). Hypoxemia was achieved by lowering maternal inspired O₂ concentration and the hypoxemia period was preceded and followed by 2 h pre-hypoxia and recovery periods, respectively. Control experiments (n=4), involving 6 h periods of normoxia were also carried out. Samples were taken simultaneously at predetermined time periods from maternal femoral arterial and uterine venous catheters for measurement of progesterone concentration. Blood flow to the uterine horn containing the operated fetus was measured continuously, and utero-placental progesterone output was calculated as the uterine venous - arterial difference in progesterone concentration times uterine blood flow. Blood samples were also collected from the fetal femoral artery and umbilical vein, and in these samples, as well as in the maternal samples, the following variables were measured: PO₂ , PCO₂ and pH, hemoglobin concentration, blood O₂ saturation and content, glucose and lactate concentrations and fetal plasma Cortisol level. The following variables were calculated from these data: uteroplacental oxygen delivery and consumption and glucose uptake and lactate flux. Maternal and fetal arterial pressure and hear [...]
doi:10.14288/1.0087079 fatcat:zhbh6ao42fdbdkokidnckl6f6y