The safety period is an integral part of a woman’s menstrual cycle and can be divided into the pre-ovulatory safety period and the post-ovulatory safety period. Pre-ovulatory safety period is the period from the cleansing of menstruation to the first three days of ovulation, while post-ovulatory safety period is the period from the end of ovulation to the next menstrual period. The post-ovulatory safety period is the period from the end of ovulation to the next menstrual period. The ovulation period is the period from 5 days before to 4 days after the day of ovulation. In women with regular menstrual cycles, the ovulation day is on the 14th day before the next menstrual period. In other words, the time outside of ovulation and menstrual period, there is basically no mature follicle discharge, that is, the safe period, and the longer the time apart from ovulation, the higher the safety factor, such as the week before and after the menstrual period, relatively safe, and for women with regular menstrual cycle, ovulation and safe period is also more regular, you can master their own safe period to contraception. But the safety period is only a relative concept, women with irregular periods and women who use sex hormone drugs may also ovulate during the safety period, so it is not recommended that such women use the safety period method of contraception. In addition, even if you are in the safe period, if you do not intend to prepare for pregnancy, you still need to combine it with other means of contraception, such as taking the pill.