Because of the brain’s rapid development, the embryo’s head is proportionally much bigger than the rest of the body. The upper limbs are developing. The heart cavities are formed and the blood is flowing. The bony structures appear and a primitive skeleton takes form. The ossification of the skull and jaws begins, muscles are developing and the external ears are formed. Although there is no tangible gender differentiation, the main development of external genitalia starts.

This week

Baby measures about 12 mm (from head to heel)
Baby weighs about 0.8 grams