The ovulation period for women is 5 days before and 4 days after ovulation day, about 10 days, and occurs in the middle of two menstrual periods, i.e. about 14 days before the next menstrual period, when intercourse has the highest chance of conception. Except for ovulation and menstruation, all other times should be considered as safe periods. Ovulation and the safety period for women are not absolute and should be judged relatively according to the regularity of menstruation. However, it is forbidden to have intercourse during the menstrual period to avoid retrograde infection and increase the chance of gynecological diseases. In addition, ovulation and menstruation are controlled by the level of sex hormones in the body, and if menstruation is regular, ovulation will be relatively regular. However, if stimulated by external factors or the use of emergency contraceptives, which affect the endocrine level, abnormal ovulation may occur during the non-ovulatory period, so the safety period is not absolutely safe. It is recommended that women pay attention to rest in daily life, do not lose weight excessively, live a regular life, be emotionally stable and avoid endocrine disorders, so as to reduce the impact of the environment on menstruation.