The effect of exposure to hypergravity on pregnant rat dams, pregnancy outcome and early neonatal development

Abstract We previously reported that hypergravity exposure affects food intake and mass gain during pregnancy. In the present study, we explored the hypothesis that changes in maternal body mass in hypergravity-exposed pregnant rat dams affect pregnancy outcome and early offspring development. Furthermore, we hypothesized that the changes observed at 1.5G will be magnified at higher gravity and by exposure during critical developmental periods. To test this hypothesis, we compared maternal body mass gain, food consumption, birth outcome and early offspring development between Sprague–Dawley rat dams exposed to graded (1.5–1.75G) chronic hypergravity (HG) or rotation (rotational control, RC) on a 24-ft centrifuge for 22.5 h starting on gestational day (G) 10 with dams housed under identical conditions but not exposed to hypergravity (SC). We also compared maternal body mass, food consumption, birth outcome and early offspring development between rat dams exposed to 1.65G during different stages of pregnancy and nursing. Exposure to hypergravity resulted in transient loss in body mass and prolonged decrease in food consumption in HG dams, but the changes observed at 1.5G were not magnified at 1.65G or 1.75G. On the other hand RC dams gained more mass and consumed more food than SC dams. Exposure to hypergravity also affected pregnancy outcome as evidenced by decreased litter size, lowered neonatal mass at birth, and higher neonatal mortality; pregnancy outcome was not affected in RC dams. Neonatal changes evidenced by impaired righting response observed at 1.5G was magnified at higher gravity and was dependent on the period of hypergravity exposure. On the other hand, righting response was improved in RC neonates. Hypergravity exposure during early postpartum affected the food consumption of nursing mothers and affected early survival of their offspring. The changes observed in dams and neonates appear to be due to hypergravity exposure since animals exposed to the rotation during the same period are not affected. This study suggests that while pregnancy can proceed under altered gravity, exposure to hypergravity affects pregnant dams, pregnancy outcome and the developing fetus as well as nursing dams and neonates and raises an important question whether the mammalian system possess a gravisensing ability.