The period between the end of menstruation and ovulation is the safe period, and the safety factor is usually higher within a week after menstruation. The entire menstrual cycle is divided into four phases: menstruation, follicular development, ovulation and luteal phase, during which sexual intercourse has a higher chance of conception, which is often referred to as the danger period. In women with regular menstruation, they have a period once every 28 to 30 days. The 14th day before the next menstrual period is called the ovulation day, and the period 5 days before and 4 days after the ovulation day is called the ovulation period. Intercourse during menstruation is usually not recommended to avoid infection. Therefore, the safe period should be the period from the end of menstruation to before ovulation and from after ovulation to before the next period, especially during the week after menstruation is relatively safest. For women who usually have regular menstruation and ovulation is relatively regular, they can use the safe period contraceptive method if they have no plans to get pregnant, but if they have irregular menstruation, it is not recommended to use the safe period contraceptive method to avoid unintended pregnancy. In addition, the calculation of the safety period in daily life is relatively troublesome. If the couple has no intention to prepare for pregnancy, they can use other contraceptive measures to prevent pregnancy, such as wearing condoms, taking birth control pills or placing birth control rings.