1. The male gamete (sperm) fuses with the female gamete (ova/egg) during fertilization to form a zygote. 2. The zygote develops into an embryo, which implants in the uterus and develops further into a fetus through the roles of the placenta and umbilical cord. 3. Childbirth occurs when contractions push the baby through the birth canal, after which the placenta detaches from the uterus and is delivered.