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

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. Retrospective cohort study. In vitro fertilization center. Single- versus double-embryo transfer. 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. Live birth, multiple gestation. 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. 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. ¿Es perjudicial para la probabilidad de nacido vivo transferir un embrión de menor calidad con un blastocisto de buena calidad? Determinar si es perjudicial transferir un embrión de menos calidad con un blastocisto de buena calidad, dado que la evidencia sugiere que los embriones pueden señalizar al endometrio y que la calidad embrionaria puede afectar a la receptividad endometrial negativamente. Estudio de cohorte retrospectiva. Centro de fecundación in vitro. Transferencia de uno versus dos embriones. Se compararon pacientes con transferencia de un blastocisto de buena calidad más un blastocisto de menor calidad, un blastocisto temprano o una mórula, con pacientes que recibieron un solo blastocisto de buena calidad. nacido vivo, gestación múltiple. En este estudio se analizaron 4640 ciclos de fecundación in vitro. En ninguno de los análisis, la transferencia de