If the ovum is fertilized during Ovulation, it will become a zygote. It will start to copy itself over and over again through mitosis. It will also move from the ovarian duct into the uterus. The levels of estrogen and progesterone in the body remain high. The zygote grows into an embryo and implants itself into the endometrium tissue of the uterus. This forms a placenta, which starts to mature.