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.
Anyway, it could start 3 days after a 3-day transfer, or the day after a 5-day transfer, depending from woman to woman. You can have menstrual-like cramping and bleeding during implantation, which is common symptom. However, often it is a silent process and most women do not experience cramps before implantation. I am telling you this although I am not a doctor, because I had long time until I finally get pregnant.