High multiple pregnancy rates after double embryo transfers in human: a retrospective cohort study.

Abstract: To improve clinical outcomes of human medically assisted reproduction, the transfer of multiple embryos is frequently performed. This leads to high rates of multiple pregnancies. In this study we explored if a cohort of patients can be defined, that benefits from the transfer of two embryos while mitigating the odds of multiple pregnancies by considering female patients' age, embryo quality and embryo cohort quality. In this retrospective cohort study, clinical pregnancy rate (CPR), live birth rate (LBR) and multiple pregnancy rate (MPR) after fresh single embryo transfers (SETs, n = 245) were compared to those after double embryo transfer (DET, n = 278). Female patient's age, embryo quality and embryo cohort quality were used to explore clinical outcomes in subgroups. Overall, this study found that compared to SET, DET significantly increased the CPR (33.5 vs 49.6%, adjusted odds ratio (aOR): 2.233, 95% CI: 1.529-3.261, P < 0.001), LBR (24.1 vs 39.2%, aOR: 2.416, 1.605-3.636, P < 0.001) and MPR (0.0 vs 25.4%, P < 0.001). Subgroup analysis based on female age, embryo quality and further stratification based on embryo cohort score revealed that the MPR in all subgroups was high after DET and a subgroup with significantly reduced MPR after DET could not be defined. In conclusion, DETs are associated with high MPRs that cannot be avoided by considering female patients' age, embryo quality and embryo cohort quality. SET is the most effective way to avoid a multiple pregnancy.

Lay summary: This study examined whether it is possible to avoid multiple pregnancies in treatments of assisted reproduction when two embryos are transferred to certain patients. Transferring more than one embryo can increase the chances of pregnancy and live birth but also raises the risk of multiple pregnancies. Multiple pregnancies are linked to health risks for both the mother and the children. Using data from a single clinic, this study explored whether there are specific patients who could benefit from the transfer of two embryos while still having a lower risk of multiple pregnancy. However, the researchers found that DETs consistently lead to high rates of multiple pregnancies, even when factors like the mother's age, embryo quality and overall embryo cohort quality are considered. The researchers concluded that transferring a single embryo remains the safest approach to prevent multiple pregnancies.