Minimal Stimulation (mini stim aka Mini IVF) – is based on the idea that lowering the amount of gonadotropins used for stimulation improves the quality of the oocytes. The downside of the minimal stimulation is a lower yield of oocytes than during a regular stimulation but for some patients, it improves the quality of the embryos.
The explanation for this improvement is usually less FSH means a less negative impact on the eggs. Indeed, it is possible that a lower FSH level would recruiter fewer granulose cells into the production of estradiol, leaving more granulose to nurse the oocyte. However, this explanation is rather weak, because ovarian stimulation regimens begin well after follicle recruitment into the cycle, and by that time the granulose would be expected to complete its differentiation. The term maturation concept provides a much more plausible explanation for the embryo quality improvement in cases of Mini IVF. With less FSH the follicles usually grow slower, extending the duration of the resulting follicular phase and making it closer to term, which would be expected to be particularly beneficial for women of advanced reproductive age.