Contrast-enhanced ultrasonography and elastography in the evaluation of the placental insufficiency in pregnant ewes exposed to insolation

Abstract

The increase in global temperature and frequent heat waves have impacted humans and animals, especially during the gestational period, when there is an imbalance in thermoregulatory mechanism. An increase in the number of premature births, stillbirths and decrease in birth weight have been reported, as well as increase risks of developing hypertensive disorders during the gestational period and increased morbidity and mortality in newborns. Domestic animals have shown low productivity and reproductive deficits such as infertility, embryonic and fetal losses and lower offspring performance. Ovine and humans share very similar adaptative mechanisms for the development of the uteroplacentary bed and support of the gestation. Therefore, the ewe is an animal model for the study of numerous gestational pathologies in humans. Placental changes are quite subtle and their detection is, in most cases, late, leading to gestational anomalies such as fetal growth restriction. Imaging modalities such as contrast-enhanced ultrasonography (CEUS) and elastography allow the detailed study of the reproductive system in different animal species. Therefore, the objectives of this proposal are: 1) Evaluate morphological and hemodynamic alterations as well as changes in maternal-fetal tissues perfusion and elasticity in sheep with placental insufficiency, using B-mode and Doppler ultrasonography, CEUS, and elastography; and 2) Test the protocol for inducing placental insufficiency due to heat stress in sheep exposed to sunlight on pasture. Prospective studies will be carried out using 14 adult sheep with 45±2 Kg. Heat stress-induced placental insufficiency will be produced by maintaining pregnant sheep (n=7) exposed to sun light from day 70 to 120 of gestation. B-mode and Doppler ultrasonography, CEUS, and elastography will be used to evaluate the uterus and placentomes of sheep with placental insufficiency, compared with the control group (allocated in a thermoneutral environment). Statistical tests will compare and correlate the data obtained for normal and altered pregnancies for each experiment. Significant results will consider p<0,05 (5%). It is expected that the heat exposure protocol proposed in this study will lead to placental insufficiency and that advanced imaging modalities will provide an early diagnosis of heat-induced placental changes. In this way, it is expected that the results produced will have direct application to increase sheep farming and can be indirectly used in studies with pregnant women, in a translational manner.