OBJECTIVE Although most embryologists load air bubbles into the catheter along with embryos during embryo transfer, the effects of these air bubbles on embryo transfer success rate are not clear. METHODS Air bubbles were nonsurgically injected into unilateral uterine horns of mice to demonstrate the negative effects of intrauterine air bubbles on embryonic development. RESULTS Our data showed that when air bubbles are nonsurgically injected into unilateral uterine horns of pregnant 4days mice the litter size is significantly decreased. Four days after the introduction of air, abnormal decidua and dead conceptuses were detected in the uterine horns receiving the air bubbles. In addition, intrauterine air also significantly impaired murine embryo transfer success rates, and induced an increase in endometrial capillary permeability and decidualization in mice on day 4 of pseudopregnancy. These results strongly indicated that the air bubbles loaded into embryo transfer catheters to bracket the embryo-containing medium may have negative effect on embryonic implantation and development. CONCLUSIONS Intrauterine air impaired murine embryonic postimplantation development, and this provided some clues for improving embryo transfer techniques in human.