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.
Implantation bleeding does not have to last a full day; you may only see one spot on your underwear or on used toilet paper, which is why some women don't even notice. It's important to keep in mind that implantation bleeding is different for everyone, and you may bleed for more than two days and still be pregnant.