Dose of recombinant FSH and oestradiol concentration on day of HCG affect embryo development kinetics.

During follicular growth, the follicle is exposed to an almost ever-changing composition of isoforms of FSH and LH, which causes a number of different and divergent biological effects. Through a time-lapse system, embryo kinetics were examined following the use of FSH only (recombinant FSH, rFSH) and gonadotrophins containing LH activity (human menopausal gonadotrophin, HMG, and FSH+HMG) in oocyte donors. No significant differences were seen between the three groups (for rFSH, HMG and rFSH+HMG, t2 was 27.8h, 27.9h and 27.5h respectively). Moreover, although embryos obtained with rFSH showed an increase in the proportions of optimal timings of development, the differences observed were not significant, as shown by the percentages of embryos inside/outside these kinetic variables. In contrast, for gonadotrophin dosage and oestradiol concentration, this study observed differences in embryo development kinetics for some of the variables evaluated, which allowed the description of an optimal range of gonadotrophin dosage and oestradiol concentration. However, these kinetic differences did not translate into important distinctions in the proportion of optimal embryos with a higher implantation potential.