Effects of embryo retention during embryo transfer on IVF outcomes

To investigate embryo retention (ER) rate in embryo transfer (ET) cycles and its effects on reproductive outcomes in a large database.

A matched retrospective cohort study in a tertiary academic hospital-based reproductive center. A total of 15,321 ET cycles were performed from January 2008 to December 2018. Each woman was matched with three separate control subjects of the same age (± 1 year), embryo condition, main causes of infertility, and type of protocol used for fresh or frozen ET cycles. The main outcomes were ER rate, and implantation, clinical pregnancy, ectopic pregnancy, and live birth rates.

The overall incidence of ER was 1.4% (213/15,321). There was no difference in the rate of ER rate in fresh ET cycles compared with frozen transfer cycles (P = 0.54). We matched 188/213 (88%) of cases in the ER group to 564 non-ER cases. There were no cases of the blood in the catheter seen in the ER group. Pregnancy outcomes were similar between the ER and the non-ER cycles: clinical pregnancy rate (31.3% vs. 36.1%, P = 0.29), implantation rate (26.2% vs. 31.3%, P = 0.2), live birth rate (20.3% vs. 24%, P = 0.53), ectopic pregnancy rate (0.5% vs. 0.4%, P = 0.18), and miscarriage rate (10.7% vs. 11.3%, P = 0.53).

Our results suggest that ER rate does not affect the reproductive outcomes including clinical pregnancy rate, implantation rate, and live birth rate. Patients and physicians should not be concerned about the retention of embryos during transfer since there is no effect on pregnancy outcome.