Main findings:
This study showed that the inclination of uterine corpus might be an
independent risk factor for the success of cleavage stage embryo
transfer population. The more the uterine corpus tended to horizontal
position, the lower the CPR and LBR of the cleavage-stage ET group.
However, blastocyst transfer were not affected by the uterine corpus
inclination. Moreover, there were no significant difference in pregnancy
outcomes between cleavage stage embryo transfer and blastocyst transfer
when the inclination of uterus was larger; when the uterus tends to the
horizontal position (small uterus inclination ), the CPR and LBR of
blastocyst transfer group were significantly higher than that of
cleavage stage embryo transfer group. These findings suggest that active
blastocyst transfer should be advised for the uterus tending toward the
horizontal position, avoiding the influence of uterine position on
pregnancy outcomes; for the patients with a uterus with greater
inclination who have fewer embryos, blastocyst transfer should be
avoided because of its non-superiority, to prevent the loss of precious
embryos in the cultivation process 17.