Fertilization occurs when an egg and sperm unite in the uterus. The uterus expands during a normal 40-week pregnancy to accommodate the growing fetus. The placenta provides oxygen and nutrients to the fetus through the umbilical cord. Labor involves three stages: cervical dilation, birth of the baby, and delivery of the placenta. It is important for the health of the mother and baby that the woman receives prenatal care during pregnancy.