ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of low and high oxygen concentration on embryo development, pregnancy outcome and birth defects offertilization-embryo transfer (IVF-ET).</p><p><b>METHODS</b>According to the oxygen concentration ofculture environment, the IVF-ET performed in the Women's Hospital, Zhejiang University School of Medicine during 2013 and 2015 were divided into low oxygen concentration group (=2036, 5% O) and high oxygen concentration group (=4617, 20% O). The rate of fertilization, good quality embryo, clinical pregnancy, ectopic pregnancy, abortion and birth defect were compared between two groups.</p><p><b>RESULTS</b>The good quality embryo rate was significantly higher in the low oxygen concentration group (<0.05). However, no significant differences were found between two groups in the rate of fertilization, clinical pregnancy, ectopic pregnancy, abortion and birth defect (all>0.05).</p><p><b>CONCLUSIONS</b>Low oxygen environment may improve the potential of embryonic development, but its impact on pregnancy outcome and birth defect is not significant.</p>
