Routine use of r-hFSH follitropin alfa filled-by-mass for follicular development for IVF: a large multicentre observational study in the UK.

The technical advance of recombinant biotechnology to manufacture FSH has resulted in a biochemically pure FSH preparation with high batch-to-batch consistency. The protein content of recombinant human FSH (r-hFSH) can be reliably quantified in mass units by size exclusion high performance liquid chromatography (SE-HPLC) enabling r-hFSH follitropin alfa (Gonal-F) to be filled and released in the vial on the basis of mass with dose variability of only +/-2% [filled-by-mass (FbM)]. Observational studies have merit in addressing the effectiveness of a new product in routine clinical practice. This non-interventional study assessed r-hFSH follitropin alfa FbM for the multifollicular stimulation of patients undergoing assisted reproduction. A total of 1427 patients were recruited in 21 centres in the UK and the mean age was 34.3 years (+/-4.48, range 18-48). Of those who started treatment, 1388 (97.3%) received human chorionic gonadotrophin and 1330 (93.2%) underwent oocyte retrieval. A total of 1213 (85%) patients had embryo transfer and in the majority of recorded cases, most embryos replaced were graded as 1 or 2 (74.6%). The ongoing clinical pregnancy rate was 29.2% per cycle and 34.4% per embryo transfer. The routine use of r-hFSH follitropin alfa FbM in normal clinical practice in IVF has been demonstrated to be effective, safe and well received by patients.