SUCCESSFUL PREGNANCY OUTCOME AFTER CRYOPRESERVATION OF ALL FRESH EMBRYOS WITH SUBSEQUENT TRANSFER INTO AN UNSTIMULATED CYCLE

Objective: To assess the pregnancy outcome of freezing and storing all fresh embryos produced in a stimulated IVF cycle and replacing them i n a subsequent nongonadotropin-stimulated cycle. Design: Retrospective study. Setting: University-associated assisted reproductive technolog y program. Patients: We studied 36 patients (age range 23 to 44 years) who underwent cryopreservation of all fresh embryos in a controlled o varian hyperstimulation (COH) cycle because of either the risk of seve re ovarian hyperstimulation (24 patients, group 1) or the presence of an endometrial lining < 8 mm in thickness (12 patients, group 2). Five hundred fifty-five embryos were generated for replacement in 63 cycle s. All embryos were cryopreserved in 1.5 M propanediol at the pronucle ar or two-cell stage, and 264 embryos subsequently were transferred in to a hormone replacement cycle (70%) or natural ovulatory cycle (30%). The average number of embryos transferred per patient was 4.2. Result s: Twenty-one clinical pregnancies were achieved, giving a pregnancy r ate (PR) of 58.3% per patient (33.3% per cycle). The live birth rate w as 50% per patient (28.6% per cycle). The implantation rate was 9.1%. Groups 1 and 2 had a similar PR per patient (58.3%). With 208 cryopres erved embryos remaining and considering the 33.3% PR per cycle, we exp ect the overall extrapolated PR to be 63.9%. Conclusions: This is the first series showing that freezing and storing oil fresh embryos produ ced in a stimulated IVF cycle and replacing them in a subsequent nongo nadotropin-stimulated cycle results in successful PRs. These results u nderlie the importance of a successful cryopreservation program in IVF and could be a possible approach to overcoming the alleged adverse ef fects of COH on the endometrium, thereby improving the chances of preg nancy when numerous embryos are obtained simultaneously.