As you near the end of pregnancy, your unborn baby is fully able to see and hear and the brain continues to develop. The kidneys and lungs continue to mature as well. By the 36th week, the baby's head may "engage" (drop into the pelvic area) - a process called "lightening." The bones of the skull remain soft to make it easier to pass through the birth canal. For many babies, the irises of the eyes are slate blue. The permanent eye color will not appear until several days or weeks after birth. Your unborn baby can suck its thumb and has the ability to cry.