Late fertilization may be due to delayed ovulation. Usually abnormal menstruation leads to abnormal ovulation, and delayed ovulation leads to late formation of the fertilized egg and late implantation. There is also a case of late fertilization. After the follicle is expelled, it can survive in the abdominal cavity for about forty-eight hours, and if there is no intercourse before forty-eight hours, there will be a late formation of the fertilized egg. The time of fertilization and the time of fertilization has a certain pattern, after the formation of the fertilized egg within seven to twelve days after the bed is completed, during this period need to pay attention to bed rest, do not overwork to avoid affecting the fertilized egg bed.