The first day of menstruation to have sex may be pregnant, but the likelihood of pregnancy is relatively small, it is recommended that the first day of menstruation to avoid coitus, can be in the end of menstruation 2-3 days coitus. Normal menstrual cycle regular women just after the first day of menstruation follicles in the growth state, has not matured, this time is not easy to ovulate, the general women in the end of the first day of menstruation coitus pregnancy possibility is relatively small. However, if a woman’s menstrual cycle is not regular, there will be a possibility of pregnancy on the first day of menstruation. It’s best not to have sex on the first day of your period because the cervix is in a dilated state after your period is over, and having sex too soon is likely to cause an infection in the uterine cavity, which will increase the chances of cervicitis and endometritis, so you can choose to have sex 2-3 days after the end of your period. You can choose to have sex 2-3 days after the end of menstruation. If you have sex on the first day of menstruation without contraception, you may get pregnant. If you suspect that you are pregnant, you need to have blood drawn for human chorionic gonadotropin (HCG) and ultrasound to determine whether you are pregnant or not.