If a woman has a regular menstrual cycle, then it is possible to get pregnant by having sex on the thirteenth day of the menstrual cycle.
Normally, a woman ovulates 14 days before her period, and if she has a regular menstrual cycle of around 28 days, then the 14th day of the menstrual cycle is the time of ovulation. In this case, if a woman has unprotected sex on the 13th day of her menstrual cycle, she may become pregnant.
Even if a woman has sex before ovulation, the sperm can survive in the woman’s body for one or two days, and if ovulation occurs during these two days, pregnancy is still possible. So women who have regular periods have a very high chance of getting pregnant if they have sex on the 13th day of their period.
If a woman has a desire to have children, she can increase the number of times she has intercourse during ovulation, thus increasing her chances of getting pregnant. However, if a woman has no desire to become pregnant, she should use contraception during this period to prevent pregnancy.