From the day IVF was introduced, the natural cycle has been one of the standard protocols for egg preparation. As medical understanding of the endocrine mechanisms of female reproduction progressed and new pituitary/ovarian-derived hormones (and their analogues) became available, clinical egg preparation protocols gradually moved towards various types of superovulation protocols and natural cycles slowly faded out of the first line of egg preparation protocols. However, things follow the “spiral” of negation. After a long period of silence, the natural cycle is now being re-recognized and given a “new lease of life”. So what are the advantages and disadvantages of the natural cycle? In a normal woman’s natural menstrual cycle, a number of eggs are recruited and grow, but only one egg is eventually expelled. This egg “goes through the motions” (lowered FSH physiology during the follicular phase) and “stands out” from the rest. Therefore, it is reasonable to believe that the only egg of the natural cycle is the “champion egg” of the whole batch of eggs of the current menstrual cycle, and that the embryo formed from it has the best developmental potential. In this sense, the natural cycle is a natural embryo selection compared to the superovulation cycle. From an endocrine perspective, natural cycles have zero (or near-zero) endocrine disturbance. It avoids the adverse endocrine effects of ovulation cycles due to the use of various hormones, which often cause menstrual disorders, weight gain, etc. This is another unique advantage of natural cycles. Combined with the “zero cost of ovulation medication”, natural cycles are unparalleled in terms of acceptability among egg preparation options. However, there are always two sides to the coin. The biggest disadvantage of natural cycles is that they are inefficient. The inefficiency is in terms of the number of embryos that can be obtained in a single cycle, not in terms of a single egg (as mentioned above, natural cycles are the most efficient for a single egg/embryo). With one master follicle in a cycle, there is a hurdle of failed egg retrieval (no eggs available), abnormal eggs, failed fertilization, failed oogenesis, etc. In particular, the timing of egg retrieval is the most difficult part of a natural cycle. In a natural cycle, the overall probability of having no embryos for transfer is up to 50%. This is unimaginable in a super ovulation cycle. Not every patient has the heart and financial resources to go through the “torture” of multiple natural cycles in the domestic medical environment. Overall, there is no shortcoming. Especially with the increasing medical understanding of female endocrine mechanisms and the improvement of laboratory in vitro fertilization-embryo culture techniques, natural cycles have a good future and it is reasonable to believe that the first successful IVF egg preparation protocol will be the final destination for egg preparation protocols.