Big medical data tells you: why is safe period contraception unreliable

The so-called safe period contraception is to calculate the days when women are prone to pregnancy by counting the number of menstrual cycle days, so as to avoid sexual life in these “dangerous” days, so as to achieve the purpose of contraception; and the days beyond the childbearing period < / P > < p > as early as 1916 during the first World War, a German doctor through the military truce “single hit” 25 pregnancies The analysis found that the days of conception ranged from the second day to the 30th day of the menstrual cycle. < / P > < p > statistics of only 25 pregnancies show that every day of the menstrual cycle is a risk period for pregnancy, and the concept of safe period will not be worked out in medicine. < / P > < p > childbearing period refers to the window period of easy pregnancy, during which unprotected sex may lead to pregnancy, which is specifically defined as ovulation day and the five days before ovulation. < / P > < p > another is that women are prone to pregnancy within a few days before and after ovulation. Specifically including 5 days before ovulation + ovulation day, a total of 6 days. < / P > < p > as for the myth that the safe period is “the first seven days and the last eight days” of menstruation, it is the result of further assuming that a woman’s menstrual cycle is the standard 28 days, and then adding a certain safety factor. < / P > < p > in fact, the luteal phase of women’s menstrual cycle is not always 14 days. Therefore, the hypothesis that ovulation 14 days before the next menstruation is the most basic premise to determine the fertility period is not tenable. < / P > < p > for example, a study in 2000 found that even in women with a very regular menstrual cycle of 28 days, only 10% of ovulation occurs on the 14th day of menstruation, 14 days before the next menstruation. < / P > < p > a new study based on medical big data, through the analysis of more than 600000 menstrual cycles, shows that many statements about menstrual cycle in clinical guidelines are wrong. < / P > < p > in the new study, only 13% of the menstrual cycle was the standard 28 days, and the average length of follicular phase and luteal phase was 15.4 days and 12.6 days, respectively. < / P > < p > in addition to the normal menstrual cycle in the current guidelines, the very short menstrual cycle shorter than 21 days accounted for 12%, and the very long menstrual cycle longer than 35 days accounted for 6%. < / P > < p > more importantly, a basic assumption of current medical guidelines for determining ovulation date is that regardless of the length of the menstrual cycle, the luteal phase is always fixed at 14 days, so ovulation always occurs 14 days before the next menstruation, and in the 28 day cycle, ovulation occurs on the 14th day of the menstrual cycle. For women with a typical cycle of 25-30 days, the average follicular phase length was 15.2 days. For women with a normal but long cycle, it was 19.5 days, and for women with a normal but short cycle, it was 12.4 days. < / P > < p > in a very short cycle, the average length of follicular phase is 10.4 days. In a very long cycle, the longest follicular phase is 26.8 days, that is, ovulation occurs on the 27th day of the menstrual cycle. < / P > < p > the luteal phase of the menstrual cycle is not always fixed at 14 days, with an average of 12.4 days, ranging from 15 to 20 days; the shortest is 8.0 days in the extremely short cycle to 12.9 days in the extremely long cycle of 36-50 days. < / P > < p > that is to say, the basic assumption of the current clinical guidelines for determining ovulation date is not tenable originally, which means that the algorithm of presumption is fundamentally wrong. 08/17/2020