Weeks 29 to 32 – 15 to 17 inches, 4 lbs. 6 oz.: These weeks see further development towards independent life: There is a rapid increase in the amount of body fat and the fetus begins storing its own iron, calcium, and phosphorus. The bones are fully developed, but still soft and pliable. There are rhythmic breathing movements present, the fetal body temperature is partially self-controlled, and there is increased central nervous system control over body functions.