The regular vacation refers to the menstruation, 11 menstruation 15 finished, the 20th coitus may be pregnant. If a woman’s menstruation is more regular, the 11th menstruation is probably within the 19th belongs to the safe period range, the possibility of pregnancy is relatively small, but at this time has reached the 20th, intercourse may be pregnant, and the chances of pregnancy may increase. If a woman’s menstrual period is not regular, the safe period and ovulation range is not fixed, at any time may produce ovulation, so the 20th coitus may also be pregnant. Safe period contraception is not reliable, if you do not plan to get pregnant, you must choose the appropriate method of contraception, such as the use of condoms. If you want to get pregnant, you need to do a good job of preparing for pregnancy.