Being aware of your menstrual cycle and the changes in your body that happen during this time can help you know when you are most likely to get pregnant. Using an ovulation calendar will help you to predict your most fertile days, and ovulation period. During ovulation a single, mature egg that developed in the ovary during the menstrual cycle is released from a follicle. When the egg is released, it is capable of being fertilized for 12 to 24 hours, and then it begins to disintegrate. You are most fertile and most likely to get pregnant two to three days before ovulation, and 12 to 24 hours after ovulation. The time of ovulation is one of the most important things a woman should understand about her body since it is the determining factor in getting pregnant and also in preventing pregnancy.