Patients undergoing IVF often ask the question: Why do I not end up with the same number of embryos when I have a good number of eggs? What are the reasons for this? Only mature eggs can be fertilized. The fertilization rate for conventional IVF is usually about 70% and for microinjection fertilization is usually 80-90%. 2. Not all eggs can be fertilized and developed into embryos, but the rate of egg cleavage is generally over 95%. Even if the eggs are fertilized and cleaved, the quality of the embryos developed can vary, and only good quality embryos can be transferred and frozen. There are individual patients who have a significantly lower fertilization rate, egg cleavage rate, and high quality embryo rate due to poor egg quality or questionable sperm quality, and sometimes there may not even be good embryos available for transfer.