http://www.child-development-guide.com/foetal-brain-development.html

By three weeks of conceiving, the brain cells begin to form at the tip of the embryo. This tube expands and it matures to form spinal cord.

After that, the tube forms the brain. The brain cells or the neurones get developed in a slow process and the neurones begin to make contacts with each other.

At this stage, the brain cells mature very quickly and nearly 250,000 cells grow in your child's brain a minute.

The growing rate decreases after a certain time when the brain makes itself ready to handle more than 40 systems. The slowdown takes place usually after the 20th week.

The brain development of the foetus is almost complete when your baby reaches the age of 6 months in your womb.

The brain gets quite mature by this time. Mostly, all the neurones that are needed for a human life are present in the brain.

During the last three months of your pregnancy, brain development reaches a high level. In this time, the neurons become more connected with each other and it makes sense in the brain of your baby.

This development ultimately develops the system of your baby’s body. It can make the foetus to have a sense of vision, movement, hearing and language.

The premature baby can hear voices. The entire nervous system is built through his foetal brain development.

By the 24th or 25th week, the foetus’s brain is remarkably developed. The neurones make their way to the cortex and it helps the foetus’s brain to mature.

The neurones send more messages to each other at this stage. This is very important because this process helps your baby’s brain function and after birth, this connectivity will help the foetus to make connections with the outer world.

The sense of to touch in your baby progresses at this stage. He becomes familiar with various sounds that he feels.

The most surprising thing is he reacts to all the sounds that he hears and his system is capable of hearing outside sounds like music.

At this stage he gets habituated with every sound. He can recognise your voice because he is very much habituated with the sound of your voice.

When he hears some sound for the first time, it makes him startle but after hearing the sound more than one time he gets habituated with the sound.