Fetal development in pregnancy week 12:fetus in third month Even though your little Einstein’s body is still growing quite rapidly 2 inches long right now, the overall super-speedy growth of their amazing brain continues to leave the head proportionately larger than the body— and is actually slightly more than one third of their total body mass! The head and neck are still straightening at this point as can be seen by their little chin lifting off of the chest. Your baby is also actively rehearsing “breathing” by using amniotic fluid to prepare the lungs for future air respiration.
The big news: your little pooper is now officially going to need diapers! Although a majority of the waste produced is transferred to the mother’s system for discharge (to avoid having it linger in the amniotic sac), some urine is released to the amniotic fluid and your baby will actually breathe it in before it passing it on to your for discharge. Not to worry, urine--in this particular form, is completely harmless to your baby.