Gestation and birth in humans

A zygote divides to become an embryo, which then develops into a foetus made of different cells and tissues. The human gestation period is about 40 weeks. The foetus grows in an amniotic sac which is filled with amniotic fluid for protection. The mother provides all the nutrients that the growing foetus needs and gets rid of waste products through the placenta. During birth, the cervix opens and the uterus wall contracts to push the baby out through the vagina.