After every holiday, gynecological clinics always usher in a wave of abortion, many people are the same question: “Doctor, I clearly see the aunt software is safe, how so unlucky will also be pregnant?” Let me tell you why safe period contraception is so unreliable! 1, first of all, the sperm is a strong Oba, after entering the body of the woman can be dormant in the fallopian tube and survive for 5 days! Not 2-3 days as stated on the internet! 2, the egg develops on the first day of menstruation, the first day of coming! Not after the end of menstruation, this is a cognitive misunderstanding of many girls! It is also the reason why some women with short cycles are also pregnant during menstrual sex! 3, theoretically: female ovulation is generally in the next menstrual period before the 14th day (is the reverse method), the egg can survive 12-24 hours after discharge. For example, the menstrual cycle of 26 days of women, the day of ovulation is the 12th day of menstruation, then the 7th day of menstruation has entered the fertile period, and this time many women’s menstruation is actually just clean. 4, the ovaries are a girl who is very susceptible to mood swings, stress, late at night, etc., happy to advance the row of eggs, not happy to strike delay ovulation, so the plain irregularity of the girls must not be based on what the great aunt software to project your safe period!