For fertilization to occur, the sperm must find the egg within one day (24 hours) of the time the egg leaves the ovary. The sperm itself survives for 2 – 3 days (48 – 72 hours) within the woman’s body. So fertilization can occur if a woman has sexual intercourse during a five – day period – one, two, or three days before ovulation, the day of ovulation, or one day after.

While still in the tube, the fertilized egg begins to divide and grow. At the same time, it continues to move through the tube towards the womb. It takes an average of five days to reach the inside of the womb. Within two days of reaching the womb, the fertilized egg attaches itself to the lining of the womb. This process is known as implantation.