If your menstrual cycle is usually very regular, once a month, the week before your period is usually in the safe period, and you have intercourse without contraception, the probability of pregnancy is relatively small, less than 15%. However, the safe period is not 100% safe, if the recent mental stress, depression, often stay up late, irregular work and rest time, may affect ovulation or even delay ovulation, before the menstruation is not necessarily a safe period, may be just in the ovulation, the probability of pregnancy is greater at this time, about 70%. If you are not planning to prepare for pregnancy in the near future, you should take strict contraceptive measures every time you have sex, you can use condoms to prevent pregnancy throughout the whole process. 40 years old women can also take short-acting oral contraceptives to prevent pregnancy, such as Yosemite, Yosemite, Daying-35 and other short-acting oral contraceptives are very effective and have very few side effects. If you don’t want to have children in the future, it is recommended to use an IUD to prevent pregnancy.