A normal person’s month is simply the 1st to the 30th, while a girl’s month is made up of the safe period, ovulation, and the aunt period. And one can’t help but wonder, what is the safe period in the end? Where is it safe? The safe period actually refers to the calculation of the regularity of the female physiological cycle, to conceive a high or low probability of exclusion, and finally to calculate a relatively safe, not easy to conceive time, this a period of time is called the safe period. The safety period is divided into the pre-ovulatory safety period and the post-ovulatory safety period. The period from the day of menstruation to the day before the start of ovulation is the pre-ovulatory safety period. From the first day after the end of ovulation to the day before the next menstrual period is the post-ovulatory safety period. Theoretically, the menstrual cycle is 28 days, and the day of ovulation is around day 14. We call the 4-5 days before and after the day of ovulation, together with the day of ovulation, a total of 10 days as the ovulation period, which is the fertile period, except for about 7 days of menstruation, the rest is the safe period. In addition, menstruation is also a safe period, but it is usually excluded because you cannot have intercourse during menstruation. For example, if you have your period from the 1st to the 7th, the 14th is the day of ovulation, and the 11th to the 20th is the ovulation period, where the 8th, 9th and 10th are the pre-ovulation safe period, and the week before your next period, which is the 21st to the 27th, is the post-ovulation safe period, both of which are collectively called the safe period. But when your period comes is like a metaphysical science, because everyone’s menstrual cycle and the length of time is different, ovulation also varies from person to person, so everyone’s safety period is not the same, if you want to calculate the quasi-safety period, first of all, we need to count the last six months of menstruation, find the longest and shortest cycle, choose the shortest cycle to calculate more accurately. For example, if your shortest cycle is 26 days, then the number of days after your period is clean is 26-21=5 days, which means that these 5 days are your safe period after ovulation, and the safe period before ovulation does not change. However, ovulation is affected by many factors, such as mood, physical state, medication, etc., so the safe period is not absolutely safe, but can only be called a relatively safe period, while the safe period can be contraceptive argument is not broken, calculate a good ovulation day, safe period, menstrual period is also in order to women can better understand themselves, and not to “make the most of It is not about “making the most of” the safe period. References: [1] Xie X., Kong B. H., Duan T. Obstetrics and Gynecology. 9th edition [M]. Beijing. People’s Health Publishing House.2018.