There are some “secret recipes” about safe period contraception circulating on the Internet – “seven before and eight after”, “three before and four after” …… I don’t know if you have heard of it, is it true? Is it accurate? So, how many days after the “period” is a safe period? Women usually have a period once a month, from the beginning of the current period to the first day of the next period, called a menstrual cycle. Theoretically, a woman has one ovulation per menstrual cycle. The so-called safe period method of contraception refers to a period of time when a woman is relatively unlikely to conceive based on her ovulation time and the time that sperm and eggs can survive in the female reproductive tract. If a partner chooses to have sex during this time, it will reduce the chances of “winning” and provide successful contraception. The safety period is divided into a pre-ovulatory safety period and a post-ovulatory safety period. The period from the day of menstruation to one day before the start of ovulation is called the pre-ovulatory safety period; the period from the first day after ovulation to one day before the next menstrual period is the post-ovulatory safety period. Generally speaking, the post-ovulatory safety period is safer than the pre-ovulatory safety period! This is because some women may be affected by environmental changes and mood swings that lead to early ovulation, so that the pre-ovulatory safety period will be shortened without their knowledge, which makes the pre-ovulatory safety period not very safe. This is why many people rush to have sex as soon as their aunt leaves, wanting to make the most of the “safe period” to enjoy the thrill of the “vacuum”, only to find out they have accidentally won the lottery. The chances of the ovaries ovulating twice in a menstrual cycle are extremely small, that is, after ovulation to the next menstrual period before the period generally does not occur again the second ovulation, so, after ovulation safe period is relatively safe. So how exactly is the safe period calculated? If you want to use the safe period contraception, the most important thing is to calculate the day, there are usually the following two calculation methods. 1, the general formula: ① women can determine the average cycle days based on the previous 6-12 months of menstrual cycles, and budget the next menstrual period date; ② expected next menstrual period day minus 14 days, is the assumed ovulation day; ③ in the assumed ovulation day 5 days before and 4 days after (a total of 10 days) for the danger period, at this time, if you do not want to If you don’t want to “win the lottery”, you should avoid “popping”; and the rest of the days are the safe period. 2, the classic modified Ogierno formula: according to the previous 6-12 months of menstrual cycle records. The shortest cycle days minus 21 days, the forward projection is the former safe period; the longest cycle days minus 10 days, the backward projection is the latter safe period. For example, in the past 6 months, the shortest menstrual cycle of a woman is 28 days and the longest is 32 days; the result is 28-21=7 and 32-10=22. Then, the first 7 days of this woman’s menstrual cycle is the pre-safe period, the 8th day is the beginning of the dangerous period, the 22nd day is the end of the dangerous period, and the 22nd day is the end of the dangerous period. After the 22nd day until the next menstrual period is the post-safe period. Have you got it? Lastly, I would like to remind you: don’t be greedy for the so-called “safe period”, because there is no absolute safe period, so every time you “fap” should be carefully protected! References: [1] Chen Yimin, Li Chao. Do you know how to calculate the safe period [J]. Health Expo. 2018(8)