A woman’s menstrual cycle is divided into: the menstrual phase, the proliferative phase and the luteal phase. Safe period contraception, a traditional form of contraception, was one of the most common forms of contraception before the invention of the pill and the IUD. According to the World Health Organization, under ideal conditions, safe period contraception still has a 5% failure rate. And that’s just for people with normal menstrual cycles; in reality, the failure rate is much higher than that. Normal women of childbearing age menstruate every 28 days, from the first day of menstruation to the first day of the next menstruation, known as 1 menstrual cycle. Generally speaking, women ovulate 14 days before the next menstrual period, after the egg is discharged, it can survive in the female body for about 1-2 days, while male sperm can survive in the female body for 2-3 days, such as couples who have intercourse 3 days before and 5 days after ovulation, the chances of conception are the greatest during this period, in addition to this period of time, are relatively safe. Each woman’s menstrual cycle is not the same, in the absence of gynecological diseases, 28 days plus or minus 7 days is the normal menstrual cycle, everyone’s menstrual cycle has its own regularity, which for the calculation of ovulation there will be a bias, if the calculation is wrong, it will lead to an increase in the chances of conception; secondly, women’s menstruation by emotions, environment and other influences, such as excessive tension or emotional excitement and other situations will affect the menstrual cycle and the time of ovulation. Ovulation time, the safe period in this case is not good to calculate. Therefore, for people with irregular menstrual cycles, safe period contraception is not recommended, because there is a possibility that your safe period is not in the real safe period, therefore, leading to the emergence of safe period pregnancy.