Abstract: To establish animal model of fetal distress in ewe,the intrauterine operations were performed on the near-term gestation sheep, and 0.5 ml microsphere （50μm in diameter） suspension at 1% concentration was injected into the fetal abdominal aorta by intravascular catheterization once at 15 minutes interval. The variations in the blood gas and blood acid-base status induced by microsphere injection in the model fetus were moni-tored. The results showed that the variations were similar to clinical signs of fetal distress in human,on the other hand，the maternal blood pH，Pco₂ and Po₂ were maintained rela-tively steady.

Key words: Sheep, Fetal distress, Microsphere, Blood gas analysis