Fertilization Fetal development starts with the process of fertilization. It starts when the female ovulates producing an egg. This egg then travels into the fallopian tube where it waits to be fertilized. Once sperm enter the body they must travel up the uterus until they make their way up to the egg. Once at the egg the sperm try to get in. They sperm wiggle their tails until they make it in. Once it makes it in the egg will not any other sperm in. The sperm that made it then drops its tail. After about twenty hours inside the egg the sperm finds the nucleus of the egg and fuses with it. Now the egg has all the genetic mate