Fertilization: Sperm Penetrates Egg. It takes about 24 hours for a sperm cell to fertilize an egg. When the sperm penetrates the egg, the surface of the egg changes so that no other sperm can enter. At the moment of fertilization, the baby's genetic makeup is complete, including whether it's a boy or girl.
Implantation bleeding is an early sign of pregnancy and only experienced by 1/3 of women. Discover when and what to look for as a sign of implantation. Implantation bleeding is an early sign of pregnancy and only experienced by 1/3 of women.
1 Timing - If you conceive you will experience implantation bleeding before your period is due, usually around 9 days after you ovulate (but can occur between 6dpo and 12dpo on average).  Duration - Implantation bleeding tends only to last for a day or two and occurs intermittently.