27th weeks
- The fetus reaches a length of 38 cm (15 inches).
- The fetus weighs about 1.2 kg (2 lb 11 oz).
- The brain develops rapidly.
- The nervous system develops enough to control some body functions.
- The eyelids open and close.
- The cochleae are now developed, though the myelin sheaths in neural portion of the auditory system will continue to develop until 18 months after birth.
- The respiratory system, while immature, has developed to the point where gas exchange is possible.