For women with regular menstruation, 7-10 days before and 1-2 days after the menstrual period is the safe period. The menstrual cycle for women is a standard cycle of 28 days, and 7 days is the standard period. The 14th day of the menstrual cycle is the ovulation day, and 7 days before the ovulation day is the follicular phase. 1-2 days after menstruation, the follicles are not yet developed, which is a safe period. The probability of conception decreases significantly, but 1-4 days after ovulation, i.e. 11-14 days before the next menstruation, there is still a possibility of conception, which belongs to the ovulation-prone period. Until 5-14 days after ovulation, the luteal function is sufficient to inhibit follicle development and enter the safe period for conception. Because the menstrual cycle is prone to fluctuations, the failure rate of the safe period contraception is high. Women who do not have the requirement to have children at the moment are still recommended to use oral contraceptives, condoms, birth control rings and other methods of contraception as a priority.