A successful pregnancy goes through many distinct stages. A man's sperm should reach, penetrate, and fertilize a woman's egg. The resulting cell must divide and form a blastocyst. The blastocyst much reach the uterus and implant in the mucous membrane. The established blastocyst continues its development into an embryo then a fetus. At any point during this process issues can occur that interfere with a successful pregnancy. 1. Fertilization Fertilization is the union of the feminine gamete (egg) and the male gamete (spermatozoa). whether or not it happens naturally within the feminine reproductive system or with the help of reproductive technologies outside of the physical body, the product is a structure referred to as a zygote. When a woman is ovulating she releases one egg into her Fallopian tubes (or additional in the case of fraternal twins). throughout this time, a woman's cervical mucus will thin, in preparation for sperm to pass through more effectively. Following spermatozoa ejaculation within the vagina