The fertile window is the time during a menstrual cycle when a person is most likely to get pregnant. It is typically around six days long and includes the five days leading up to ovulation, the day of ovulation, and the day after ovulation. The fertile window can vary depending on the length of a persons menstrual cycle, which can vary among women. To determine the fertile window, it is important to track ovulation, which typically happens about 14 days before the start of a new menstrual cycle. There are several methods to track ovulation, including the calendar method, cervical mucus method, and basal body temperature method. The calendar method involves tracking the length of menstrual cycles and calculating the fertile window based on the average length of the menstrual cycle. The cervical mucus method involves monitoring changes in vaginal discharge, which peaks 1 to 2 days before ovulation. The basal body temperature method involves tracking changes in body temperature, which rises slightly after ovulation. It is important to note that natural family planning is a less reliable form of contraception and does not protect against sexually transmitted infections.