Fertilization begins about 12 hours after ejaculation during ovulation, and the process of fertilization takes about 24 hours, and a fertilized egg is formed if fertilization is successful, so it takes about 36 hours from ejaculation to the formation of a fertilized egg. There are many complex physical and chemical processes involved in this process, and an accident at any one of them can affect the normal formation of a fertilized egg. After the fertilized egg is formed, it travels to the uterine cavity after about 5-7 days and buries itself in the uterine lining to complete the process of implantation and successful conception. If the lining of the uterus is thin, or if there is inflammation in the fallopian tubes, etc., which causes the fertilized egg to run slowly and not to be able to properly attach to the uterine cavity, tubal pregnancy or biochemical pregnancy may occur, and conception may be unsuccessful. In order to improve the chances of normal conception, it is recommended to have a comprehensive health checkup before getting pregnant, and quit smoking, alcohol, exercise, take folic acid tablets, etc. to implement the preparation for pregnancy.