Getting pregnant during menstruation is possible but unlikely. Pregnancy occurs when sperm fertilizes an egg during the fertile window, which typically occurs 5 days before ovulation through the day of ovulation itself.
During a typical 28-day cycle, menstruation usually lasts 3–7 days, and ovulation typically occurs around day 14. This timing makes pregnancy during active bleeding uncommon, since ovulation hasn't yet occurred.
However, several factors create exceptions:
Shorter cycles: If you have a cycle shorter than 22 days, ovulation may occur soon after menstruation ends, overlapping with the tail end of bleeding when sperm could still be viable.
Irregular cycles: Unpredictable ovulation timing makes it harder to identify safe windows.
Sperm longevity: Sperm can survive 3–5 days in the reproductive tract, so intercourse during your period could theoretically result in fertilization if ovulation occurs shortly after.
Bleeding confusion: What appears to be a period might be implantation bleeding or other bleeding, making actual cycle timing unclear.
While the risk is lower during menstruation compared to mid-cycle, it's not zero. If you want to avoid pregnancy, barrier methods (condoms) or hormonal contraception work regardless of cycle timing. If you're trying to conceive, tracking ovulation through methods like basal body temperature, cervical mucus changes, or ovulation predictor kits provides more reliable guidance than relying on cycle day alone.