Ovarian Stimulation with Urofollitropin (uFSH) results in a lower yield of oocytes compared to recombinant FSH (rFSH), nevertheless, uFSH is at least as effective as rFSH in younger patients: preliminary results of a retrospective study with antagonist protocols in an IVF/ICSI program

ABSTRACT

Differences in the mode of action between recombinant FSH (rFSH) and urinary derived FSH (uFSH) have been reported in cycles down-regulated by agonists. The aim of our study was to determine, if these differences also exist in cycles down-regulated by antagonists.

Antagonist cycles performed between 2009 – 2012 were divided into two groups:

1. Cycles stimulated with rFSH preparations: Follitropin alfa (n=203) and Follitropin beta (n=443) and 2. Cycles stimulated with Urofollitropin (n=405).

Cetrorelix or Ganirelix were used as antagonists. All patients received 75 IU hMG additionally from day 6 of stimulation onwards up to the day of hCG administration.

A logistic regression analysis was conducted to find the most significant parameters predicting hCG-positive pregnancy for 2471 IVF cycles. The results demonstrated that the predictors such as age of patients and number of cycles ever performed made negative contributions and number of oocytes retrieved and number of embryos transferred made positive contributions to prediction. Taking this into consideration, comparable groups could be created by including only firstever IVF cycles with more than 10 oocytes retrieved and 2 embryos transferred. Thus, the final sample for comparison included 98 patients in the rFSH-group and 27 patients in the uFSH group.

There were no differences in basic personal data and gonadotropin consumption between the groups. Stimulation with rFSH resulted in a higher yield of oocytes compared to uFSH (15,6 vs. 14,4), however, the results of the following reproductive outcome parameters were all in favor of uFSH when rFSH and uFSH were compared: oocyte maturation rate (76.5% vs. 79.0 %), fertilization rate (53,6% vs. 58,6%), embryo score 4 rate (25,7% vs.. 31,1%), hCG-positive pregnancy rate (43,9% vs. 59,3%), clinical pregnancy rate (33,7% vs. 44,4%), embryo-cryopreservation rate (19,3% vs. 30,5%) and abortion rate (14,0% vs. 12,5%).

These results seem to support the concept that uFSH produces fewer oocytes than rFSH, but the oocytes produced by uFSH are, on an average, of better quality than those produced by rFSH. Basic studies have shown that different FSH isoforms with different elimination kinetics in the two gonadotropin preparations could be responsible for the different effects.

However, the results have to be confirmed by well designed prospective randomized studies.

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