Is transferring a lower-quality embryo with a good-quality blastocyst detrimental to the likelihood of live birth?

Objective: To determine if transferring a lower-quality embryo with a good-quality blastocyst is detrimental, given that evidence suggests that embryos can signal the endometrium and that embryo quality may affect negatively endometrial receptivity. Design: Retrospective cohort study. Setting: In vitro fertilization center. Intervention(s): Single-versus double-embryo transfer. Patient(s): Patients with a double-embryo transfer of a good-quality blastocyst plus a lower-quality blastocyst, early blastocyst, or morula were compared with patients receiving a single good-quality blastocyst. Main Outcome Measure(s): Live birth, multiple gestation. Result(s): In this study, 4,640 in vitro fertilization cycles were analyzed. In none of the analyses did transferring a second lower-quality embryo negatively affect birth rate. In the primary analysis, transferring a second lower-quality embryo increased live birth by 10% and the multiple birth rate by 15%. The addition of a fair-or poor-quality blastocyst or early blastocyst markedly increased the twin birth rate by 22%-27% with an 8%-12% increase in live birth. The addition of a morula did not increase live birth but resulted in 12% more multiples. In women younger than 38 years, adding a lower-quality embryo increased the birth rate by 7% but resulted in 18% increase in multiples. In women 38 years or older, adding a lower-quality embryo increased the live birth rate by 9% with a 15% increase in multiples. Conclusion(s): Addition of a lower-quality embryo does not have a detrimental effect on a good-quality blastocyst and results in a small increase in live births. However, this is at the expense of a marked increase in the likelihood of multiple gestations. (C) 2020 by American Society for Reproductive Medicine.