If you have a regular menstrual cycle, you are in the safe range to have intercourse three days before your period and you will not get pregnant. So, if you have intercourse before three days and your period comes on schedule, this situation indicates that you are not pregnant. However, there are some women whose ovulation period is affected by many factors, such as late nights, stress, mood swings, and changes in the environment, which cause ovulation to be delayed, so they may also become pregnant. If your period doesn’t come on time after intercourse, you should be patient and wait until half a month after intercourse to take a urine test to rule out whether it has anything to do with pregnancy. It is recommended to use reliable contraceptive methods during intercourse, such as short-acting contraceptive pills or condoms. If there is a need for long-term contraception, you can use an intrauterine device (IUD). These methods are simple, safe and reliable, and the success rate of effective contraception can reach more than 90%, do not advocate the application of safe period contraceptive methods.