The first three days of menstruation can be pregnant without contraception, but the chances of pregnancy are relatively small for women who have regular menstrual cycles, and the chances of pregnancy increase if menstruation is not regular.
For women with regular menstrual cycles, although the first three days of menstruation in the safe period pregnancy chances are smaller, but the entire menstrual cycle does not have an absolute safe period, if the woman due to mental stress or a combination of polycystic ovary syndrome, etc., will lead to irregular ovulation, if at this time there is a mature egg discharged, and the combination of sperm will be pregnant.
For women in the ovulation period, the chance of pregnancy after sex is relatively large, so for women who have the need for pregnancy, ovulation test paper or ultrasound to monitor ovulation; for women who do not have the need for childbearing, do not take a chance, you need to actively contraceptives through the condom, IUD and other safe ways.