Can a women be pregnant on her period?

Difficult: It's difficult to achieve pregnancy while on a true menstual cycle since ovulation was at least 2 weeks prior and the endometrium is shedding. However, a woman can be pregnant and experience menstrual-like bleeding in the first trimester and not realize she's pregnant. This happens all the time, it's called a threatened ab. Check a pregnancy test if you have any concerns and take good care.