Menstruation and PregnancyA woman’s menstrual cycle is the number of days from the start of one period to the start of the next period. The average menstrual cycle for most women is 28 days. But for many women, a normal range can be anywhere from 21-35 days. It is also normal for the number of days in a woman’s ovulatory cycle to vary from month to month. In fact, one study of 2,700 women found that only one woman had consistent 28-day cycles over the course of a full year. The best way to determine your average cycle length is to keep a log indicating the start date for each period. The first day of a period is the first day you experience full flow, not spotting. This information can help doctors to assess your ovarian function with greater precision. A woman is fertile for only a short window of time each month – around ovulation. Keeping track of your menstrual cycle can also help you to identify the period during your cycle when you are most likely to ovulate. Doctors generally recommend that couples have intercourse starting three to four days prior to expected ovulation and up to two days after expected ovulation. This represents the period during the ovulatory cycle when a woman is most likely to get pregnant. Most fertility experts recommend that a couple have intercourse at least every 48 hours around the time that ovulation may occur to maximize the chances of achieving a pregnancy. More frequent intercourse during this period may increase a couple’s chances of getting pregnant.