The influence of supernumerary embryos on the clinical outcome of IVF cycles

Purpose: To assess the influence of the presence of quality supernumerary e mbryos on the clinical outcome and risk of multiple conception in patients having their first in vitro fertilization (IVF) cycle. Methods: Retrospective cohort study of 1448 women having their first IVF tr eatment cycle who received 4004 embryos where at least six embryos were ava ilable for transfer treated in an Assisted Conception Unit based in a large teaching hospital. Results: The replacement of three rather than two embryos to women under 35 years who had good-quality supernumerary embryos resulted in a higher twin (12.5 vs. 11.9%) and triplet birth rates (2.1 vs. 0%), without significant ly improving the clinical pregnancy (50.5 vs. 45.2%) or total live birth ra tes (38.9 vs. 35.7%). In the absence of quality spare embryos, these women who had three rather than two embryos replaced had a significantly higher c linical pregnancy rate (39.3 vs. 28.8%; P = 0.04), total live birth (32.7 v s. 19.4%; P = 0.02) and singleton birth rate per cycle (20.8 vs. 14.4%; P = 0.04), without significantly influencing the multiple birth rate. In women over 35 years, the replacement of three instead of two embryos in the pres ence or absence of quality supernumerary embryos led to a significant impro vement in clinical outcome, without being associated with a concurrent incr ease in the multiple birth rate. Women in both age groups who had either tw o or three embryos replaced in the presence of quality supernumerary embryo s had a notably better clinical outcome compared with their counterparts wh o had the same number of embryos replaced bur with no quality embryos to sp are. Conclusions: The presence of good-quality supernumerary embryos can De used as a reference to determine the optimal number of embryos to transfer and as an indicator of the probability of success of an individual couple in a given cycle. Optimal pregnancy rates and simultaneous reduction of multiple gestation can be achieved with a flexible embryo replacement policy that i s based on embryo quality, maternal age, and the presence or absence of sur plus quality embryos.