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 > or =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 concept after cryopreservation and thawing was similar to that of controls. However, prolonged coasting (> or =3 days) had a subtle negative impact on the post-thaw survival rate.