The "safe days" for a woman after her period—days on which the chance of pregnancy is lower—depend on her menstrual cycle length and regularity. Generally, the menstrual cycle starts on the first day of the period, and ovulation happens about 14 days before the next period. For a regular 28-day cycle, the fertile window usually falls between approximately days 9 and 16, so the safe days are typically the first 8 days after the period starts and days after day 16 until the next period. However, it is important to note that:
- Pregnancy can still occur soon after the period ends, especially if the cycle is short or irregular, because sperm can survive up to 5-7 days in the reproductive tract.
- No days are completely safe for avoiding pregnancy without contraception.
- The "safe period" method requires careful tracking of menstrual cycles over months to estimate the fertile and non-fertile days accurately.
- Using contraception is the most reliable way to prevent pregnancy.
A commonly used natural method defines safe days as the first 7 days after the period starts and the days starting about 7 days before the next period, avoiding the mid-cycle fertile window. Yet, this method is not 100% reliable. In summary:
- Fertile days are around day 9 to 16 if the cycle is 28 days.
- Safe days are generally before day 9 and after day 16 of the cycle.
- For irregular cycles, fertile days and safe days can vary.
- Sperm survival and early ovulation make pregnancy possible shortly after periods.
Thus, "safe days" after periods depend on cycle length, and no period days are completely risk-free without contraception.