Effect of coasting on the implantation potential of embryos transferred after cryopreservation and thawing

Objective: To examine the effect of withholding gonadotropins on the outcome of embryos after cryopreservation and thawing. Design: Retrospective clinical evaluation of patients having cryopreserved-thawed ET trials with coasting during the corresponding ovarian stimulation cycle. Setting: Academic tertiary clinical care unit. Patient(s): Patients with cryopreserved embryos having coasting in their fresh IVF cycle and age-matched controls without coasting, both groups receiving the same stimulation protocol (long GnRH agonist plus recombinant FSH). Intervention(s): All patients had a cycle in which embryos were transferred fresh and a cycle of thawing of cryopreserved embryos with the aim of transferring in a steroid-supplemented cycle. Main Outcome Measure(s): Embryo survival, implantation, and clinical pregnancy rates. Result(s): Post-thawing embryo survival (66.4% vs. 73%), implantation (12.3% vs. 13.0%), and clinical pregnancy rates (31.5% vs. 38.0%) were similar in study and control groups, respectively. Patients with coasting for >= 3 days had significantly lower post-thawing embryo survival rates compared with patients having shorter duration of coasting (< 3 days) and controls. Implantation and pregnancy rates, however, were similar in the three groups. Conclusion(s): Coasting did not seem to have a detrimental effect on oocyte and embryo quality because the implantation competence of transferred concepti after cryopreservation and thawing was similar to that of controls. However, prolonged coasting (>= 3 days) had a subtle negative impact on the post-thaw survival rate.