If the usual menstrual cycle is regular, the cycle of 28-30 days or so, the number of days of menstruation within 7 days that is, 7 days can be clean, 3 days after the clean menstruation is generally in the ovulation period, intercourse is possible pregnancy, the probability of pregnancy is about 50%-60%, or relatively large, so if there is no fertility requirements it is best to use condoms throughout the good contraceptive measures. If the intercourse does not do a good job of contraception can take oral emergency contraceptive pills to prevent unintended pregnancy to remedy, you can take oral Yutin or gold Yutin, but each sexual life after taking the pill is recommended to do a good job of contraception, because the emergency contraceptive pill is only a remedial drug, for the previous sex has a certain remedial effect, but for each subsequent sex has no regular contraceptive effect, the success rate of the remedy is about 85%. The success rate is about 85%.