Theoretical Backgrounds of the Natural Cycle and Other Minimal Stimulation Cycles: From Follicle Observation to Embryo Transfer

Abstract

The term minimal stimulation cycle encompasses a variety of ovulation stimulation methods, from the natural cycle, in which no ovarian stimulation medication is used, to the Letrozole (Femara) cycle, in which a follicular stimulatory effect is thought to take place among some patients, including those with polycystic ovary syndrome (PCOS), although its efficacy with regard to ovarian stimulation is not clear, to the Clomiphene citrate cycle, in which a definite ovarian stimulation efficacy has been demonstrated and the development of more than one follicle is normally observed. Furthermore, cycles where follicle-stimulating hormone (FSH) and human menopausal gonadotropin (hMG) drugs are used in combination at lower-than-usual levels are generally included in the minimal stimulation cycles. This chapter discusses the protocols which maximize the benefit of each method, based on the accurate evaluation of hormonal levels and clinical outcomes.