I used to worry constantly if my baby's brain was developing properly, so I totally get your curiosity! The brain actually starts forming very early, around the 3rd or 4th week itself. Just make sure you are taking your folic acid daily as prescribed by your doc, it helps a lot.
The brain and neural tube begin developing right from the first month of pregnancy. It continues to grow and mature throughout all nine months. Eating foods rich in DHA, folic acid, and iron is very beneficial for this development.
The baby's brain and nervous system start developing in the first month itself, which is why early care is so crucial. Please ensure you never miss your daily folic acid tablets and keep regular appointments with your doctor.
It starts from the early weeks itself, dear. My doctor told me to eat soaked almonds, walnuts, and green leafy veggies for good brain growth. Just follow your gynac's prescription for folic acid, that is most important.