It is recommended as an alternative to patients with particularly poor response to ovarian stimulation, such as patients with several previous failed attempts and embryos of bad quality. The development of the follicle and the endometrium is monitored with a series of ultrasounds and hormone measurements. The disadvantage of the natural cycle is that we place our hopes in one follicle from which we have to retrieve one egg that needs to be mature and fertilize normally, divide on time and create an embryo of a satisfactory quality to proceed with an embryo transfer. Of course, in the natural cycle, there is also a chance of a premature LH surge and follicle rupture that would lead to failed oocyte retrieval.