Aunt, also known as menstruation, menstruation gone a few days is the safe period, there is no specific standard, each woman’s menstrual cycle, the number of days of menstruation is different, the safe period time is not the same. Women’s usual menstrual cycle is 28~30 days, the number of days of menstrual bleeding is 3~5 days, 7 days after the clean menstruation is safer, 7 days after may enter the ovulation period. A woman’s menstrual cycle is 21~25 days, the number of days of menstrual bleeding is 7~8 days, 1~2 days after her period is clean is probably the safe period, after that she will enter the ovulation period, and the safe period is shorter. It is not accurate to project the safe period after the menstrual period is clean, it should be projected specifically in conjunction with the menstrual cycle and menstrual period. The process of female ovulation can be affected by emotions, health, external environment and other factors have delayed or advanced, may also occur additional ovulation, safe period contraception is not reliable.