Hypoxia and Oxidative Stress Are Associated with Reduced Fetal Growth in Twin and Undernourished Sheep Pregnancies

Simple Summary Twin gestations in sheep are economically more important than single ones; however, twins are born with lower weight, resulting in higher mortality and lower postnatal growth. Chilean Patagonia is very important for sheep production, but its harsh environment results in low food availability and cold and windy conditions during gestation and lambing periods, with a consequent great mortality of twins (~40%). We postulate that the restriction of fetal growth in twin and undernourished sheep pregnancies is associated with fetal hypoxia and oxidative stress. To prove this, single- and twin-bearing ewes were maintained under Patagonian field conditions and offered only natural pasture (undernourished) or natural pasture plus concentrate supplementation (well nourished). Near term, blood gases and oxidative status were evaluated in cord blood, and fetal biometric traits and placental weight were obtained after cesarean section. Both maternal undernutrition and twinning led to decreased oxygen supply to the fetuses, which was associated with decreased intrauterine growth. Moreover, twinning increased oxidative stress at the feto-placental unit, which might also contribute to the restriction of fetal growth. These results highlight the importance of maternal nutrition, especially for those ewes bearing multiples, and opens new possibilities for nutritional or antioxidant interventions for preventing fetal hypoxia and oxidative stress.