Clinically, endometrial thickness of 9mm does not necessarily mean that ovulation has occurred. During ovulation, the endometrial thickness must be at least 9mm before a fertilized egg can be fertilized. It is not scientific to decide whether ovulation is the time of ovulation simply by looking at the thickness of the endometrium, as some people have a relatively thin or thick endometrium, and clinically the endometrium should be at least 9mm in the case of normal menstruation. This may also be caused by past history of uterine operations resulting in uterine adhesions.