No. It is a mistake to think that if you have unprotected sex during menstruation, it is impossible to get pregnant. Although this is unlikely to happen, it is absolutely possible.
Most women have normal menstrual cycles, which are 28 to 32 days long. In these cases, pregnancy is rare during the period.
However, some women have short menstrual cycles (less than 25 days) and ovulation and menstruation may coincide. These women can get pregnant by having unprotected sex during the menstrual phase.