When menstruation occurs four or five days earlier, ovulation also occurs four or five days earlier. For women with regular menstruation, ovulation occurs about 14 days before the next menstrual period. When a woman’s menstruation is advanced, it indicates a change in the pattern of ovulation as well as in the hormonal profile of the body. For women who have regular menstruation, ovulation occurs 14 days before the next menstruation, so if the menstruation is advanced by four or five days, ovulation will also be advanced by four or five days. However, some people with endocrine disorders, ovulation and the production of menstruation do not have a clear correlation, you can not determine the ovulation period through menstruation. It is recommended to use adequate contraception when having sex if there is no need to prepare for pregnancy in order to prevent unwanted pregnancies. If there are abnormalities such as persistent changes in menstruation, it is necessary to go to the hospital in a timely manner and take standardized methods of treatment under the guidance of the doctor.