Some parts of your baby are now fully developed--like his hands, which are tiny but perfectly formed, although the nerve connections to the brain that will make those hands nimble are still to come. The baby's cerebral cortex, the part we usually think of when we think of the brain, is now the primary visible structure. This region of the brain is responsible for reason, planning, emotion, and problem solving. As it develops, it will continue to add numerous irregular folds and wrinkles. This augments the amount of usable area in the brain and enhances communication between the nerves.

As his nervous system and brain develop and his senses sharpen, your baby is probably reacting more to stimuli from outside the womb, especially sounds. Loud noises may stimulate a bout of kicking and squirming. If you could see him, he might even be putting his tiny hands over his ears!