The principle of natural cycle treatment is to take the spontaneously developing egg and fertilize it with microinjection. In this application, the follicle developing in the natural cycle is monitored without administering any medication and the oocyte obtained from this follicle is used for IVF/ICSI. The ‘high quality and single embryo’ formed in this way   is transferred and better pregnancy rates can be achieved. The cases to be taken into the natural cycle are determined on the third day of their menstrual cycle with ovarian capacity, ultrasonography and hormone parameters. It is the preferred method in cases with weak responses. A developing follicle (the structure observed in ultrasonography and containing the oocyte) is monitored   ultrasonographically   . The aim is to obtain the oocyte that has completed its maturation by determining the LH peak (the hormone that matures the egg and ensures cracking) approximately 24 hours after the peak when the egg size exceeds 16.5 mm and by performing the egg collection process (oocyte pick-up). The second method is to perform egg collection after 34-36 hours without waiting for the LH peak, if the follicle size is 16.5 mm or more, by giving a trigger shot called HCG.   In the Modified Natural Cycle application, when the largest follicle reaches 12-14 mm, gonadotropin and GnRH antagonist are added until the follicle size reaches 16.5 mm and the trigger shot called HCG is given. After this stage, egg collection is performed after 34-36 hours. The classical IVF process begins. After the maturity (maturation) of the obtained oocyte is evaluated, microinjection is performed. After 16-18 hours, it is determined whether fertilization has occurred. After fertilization has occurred, embryo development is monitored and the developing embryo is transferred into the uterus. 12 days after the transfer, whether pregnancy has occurred is determined by the beta HCG value in the blood. Cases with poor ovarian response have decreased pregnancy rates compared to cases with normal response. Age and the number of oocytes collected are the two most important factors determining pregnancy rates in low ovarian response. In cases with reduced ovarian capacity, the natural cycle method can be used to increase the chance of pregnancy. In some studies, it has been suggested as a valid and valuable approach in cases with poor response due to similar pregnancy and implantation rates with other stimulation protocols. However, a 50% cycle cancellation rate, 18% per embryo transfer and 10% pregnancy rates per cycle have been given. When considered as a whole, this method is an option with very low physical stress and financial costs in the treatment of cases with poor response.