Stages Of Baby Formation. Around the 5 week mark, your baby's heart will begin to beat, at 27 weeks they'll have regular sleep and wake cycles, and at 39 weeks your. Once cell differentiation is mostly complete, the embryo enters the next stage and becomes known as a fetus.
The brain is evolving quickly so the baby can see and hear, although the respiratory system requires maturation. The main stages of fetal development can be divided into three broad categories, conception, embryonic development and finally fetal development: Maintaining good nutrition and health by the mother.