Ultrasonographic pregnancy detection and inhalation anesthesia in the gray short-tailed opossum (Monodelphis domestica)

Female gray short-tailed opossums (Monodelphis domestica) with known breeding dates were anesthetized with isoflurane for ultrasonographic pregnancy detection. Beginning on gestational day 9, gravid females could be identified using a 9-MHz mechanical sector-scanning transducer equipped with a standoff pad. Fluid-filled Vesicles 3 to 4 mm in diameter were seen within the thick-walled uteri on gestational days 9 and 10. Visualization revealed loss of individual vesicles, with replacement by thick, irregular uterine walls and some free luminal fluid by gestational days 12 and 13. On the basis of subsequent birth of pups, sonographic diagnosis of pregnancy was accurate in 27 of 28 opossums examined