It's more likely to occur on the fertile days, even though the average woman won't know when these days are. For women with day menstrual cycles, ovulation usually occurs between days 13 to Pregnancy is technically only possible during the five days before ovulation through to the day of ovulation. If a woman has sex six or more days before she ovulates, the chance she will get pregnant is virtually zero. Physical signs of ovulation may vary for each woman, but may include light spotting, abdominal cramping, breast tenderness, and bloating. Previous research has shown that the five days leading up to ovulation and the day of ovulation are the days in a woman's menstrual cycle when she is most fertile. If you have shorter cycles, say 21 days between periods, ovulation happens on day 7 and the most fertile days are days 5, 6, and 7. Ovulation happens about two weeks before the next expected period. Women are most fertile during ovulation, when a woman releases an egg to be fertilized. Fertile Days in Menstrual Cycles Fertile days vary from woman-to-woman, depending on the length and regularity of her menstrual cycles. Charting your BBT can help you detect patterns of ovulation. Take your temperature the first thing each morning. Physical Signs of Ovulation. Tracking your ovulation Work out the length of your average menstrual cycle. But neither of these biological mechanisms has been established in humans. Couples should try to have sex at least every other day. Changes in Cervical Mucus.