Success of frozen embryo transfer: Does the type of gonadotropin influence the outcome?

OBJECTIVES: To determine whether there is a difference in outcome between different ovulation-induced cycles after frozen-thawed embryo transfer (FET). METHODS: We searched the Cochrane Menstrual Disorders and Subfertility Group’s trials register in May 2009, the Cochrane Central Register of Controlled Trials (Cochrane Library, Issue 1, 2008), ISI Web of Knowledge (1985 to August 2009), and reference lists of articles. Relevant conference proceedings were hand-searched and researchers in the field were contacted. Randomized controlled trials and retrospective studies were included, comparing the various cycle regimens and different methods during FET in assisted reproductive technology, ie, in vitro fertilization and intracytoplasmic sperm injection. RESULTS: Using the agonist long protocol for downregulation, five trials provided extractable data for live-birth rates, ongoing pregnancy, and clinical pregnancy rates following FET. One trial provided extractable data for clinical pregnancy rate. There was no evidence of a significant difference in any outcome between the users of urinary gonadotropins versus recombinant follicle-stimulating hormone. Data on implantation and miscarriage rates following FET were not available for analysis. CONCLUSIONS: It seems that clinical pregnancy rate after FET is not influenced by the type of gonadotropins used. Research should be directed towards improving freezing and thawing techniques.