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.
In most women implantation cramping occurs around 7 days before the missed period. Yet another difference between the pain due to implantation and menstrual cramps is scanty bloody discharge. It looks like spotting and can last for as many as two days or as few as five minutes.