Effects of hypoxia on early pregnancy and embryonic development in the mouse

The efficacy of gestation during early pregnancy was investigated in mice exposed to either 14% or 7% oxygen environments. At Day 8 postinsemination, animals were killed and reproductive tracts were examined. Embryonic development was decelerated and an increased frequency of embryo death and resorption was apparent. At the 7% oxygen level, implantation was almost always blocked as evidenced by free blastocysts and uterine debris of embryonic origin. This blockage of nidation is attributed to altered progestational support due to ovarian luteolysis as demonstrated by decreased uterine volumes. These studies indicate that reproduction is impaired by hypoxia during preplacental stages. Abnormal gestation may be attributed to the direct effects of hypoxia on the conceptus and to its indirect effects which alter the tropic and endocrine support provided by the maternal system.