Xu J, Yin MN, Chen ZH, et al. - Via performing a matched retrospective cohort study of a total of 6,089 embryo transfer (ET) cycles performed from January 2013 to December 2018 in their unit, researchers here examined the embryo retention (ER) rate in ET cycles and its effects on reproductive outcomes. Observations revealed the overall ER incidence of 1.59% (97/6,089). In fresh ET cycles, there was significantly increased ER rate compared with frozen transfer cycles (2.71% vs 1.08%). They suggest a correlation of ER rate with mucus on or in the transfer catheter in fresh transfer cycles. Retained embryos are linked with lower implantation, clinical pregnancy, live birth, and enhances the risk of ectopic pregnancy.