In the case of more regular menstrual cycle 12 days before menstruation to about 7 days after menstruation is the safe period, if the menstrual cycle is not regular, the safe period can not be determined. Ovulation is the 14th day before the next menstrual period, three days before and one day after the day of ovulation is the easiest time to get pregnant, so in addition to these days of other times are considered safe period, safe period coitus fertilization chances are relatively small. However, if the menstrual cycle is irregular, the ovulation period can not be determined, the safe period is also uncertain, there is no absolute safe period, so you can not rely on the safe period contraception. Contraceptive measures are divided into many kinds, including intrauterine devices, condoms, birth control pills, etc., of which the most unsafe is the safe period. If you do not plan to have children for the time being, it is recommended that you adopt a safe and effective contraceptive method that suits you.