A female egg cell is a part of a woman's body. A sperm is a part of a man's body. Neither egg nor sperm is a new human and both egg and sperm die a "natural death" after a relatively short time. But a fertilized egg is a new organism of its own with a new unique set of DNA that will survive the woman and the man if allowed to continue living in their proper environment.
You do not come from a fertilized egg - you have been one!
You do not come from an embryo - you have been one!
You do not come from a fetus - you have been one!
You do not come from a child - you have been one!
The fertilized egg is actually a small, completely undeveloped human being. That's how our lives began. To respect human dignity is to respect all people, regardless of age, size, degree of development or degree of dependence.