The factors affecting the outcome of frozen–thawed embryo transfer cycle

ObjectiveTo determine the impact of the clinical and embryological factors on the pregnancy outcome of frozen–thawed embryo transfer.Materials and MethodsThe data of 247 frozen–thawed embryo transfer cycles were assessed at Royan Institute from March 2006 to March 2008. Appropriate statistical analysis was performed using Student t test and Chi-square or Fisher exact test. Forward logistic regression was done to predict the individual impact of factors on the success of frozen embryo transfer.ResultsAccording to our results, 1,523 frozen embryos were thawed with a survival rate of 79.8%. The overall chemical and clinical pregnancy rates per embryo transfer cycle were 28.1% and 26.3%, respectively. A total of 71 gestational sacs were implanted (7.9%). The pregnancy outcome was higher in women who were stimulated with the gonadotrophin releasing hormone agonist long protocol, treated by a combination of follicle stimulating hormone and luteinizing hormone, who had endometrial thickness greater than or equal to 8 mm on the embryo transfer day, and who had positive fresh-cycle pregnancy test.ConclusionProtocol type, gonadotrophin preparations, fresh-cycle outcome, endometrial thickness and the numbers of obtained oocytes, embryos, and high-quality thawed embryos transferred are the factors affecting pregnancy outcome of frozen–thawed embryo transfer.