A woman can get pregnant any day of the month if she has unprotected sex with a man. However, there are only a few days each month when she is actually fertile and able to conceive.
The average menstrual cycle is 28 days long, but it can range from 21 to 35 days. ovulation usually occurs around day 14 of the cycle, but it can occur as early as day 10 or as late as day 20. This means that a woman can be fertile for up to 10 days each month.
However, not every sexual encounter will result in pregnancy. There are many factors that contribute to fertility, including the quality of the sperm and egg, timing of intercourse, and the health of both partners. In general, about 25% of sexual encounters will result in pregnancy.
So, while a woman can technically get pregnant any day of the month, her chances are highest during the few days leading up to and including ovulation. If you're trying to conceive, have regular unprotected sex during this time period for best results.