This does not happen on the same day. At one stage of the endometrial cycle, the endometrial lining suitable for implantation is 7-8 days after ovulation. After ovulation, if the egg and sperm can successfully form a fertilized egg, 7-8 days after the formation of the fertilized egg is the most suitable date for the fertilized egg to implant, and the endometrium is the most suitable soil for implantation at this time. If the egg does not successfully implant at the most suitable date for implantation, the endometrium will shrink in the following 7-8 days, and accordingly, with the shrinkage of the endometrium, menstruation will occur. So by the correlation between the endometrium and ovarian ovulation it is understood that the date suitable for implantation and menstruation will not be on the same day.