The baby is now about 17 inches long, weighs 4½ pounds and continues to grow and mature. By this stage of development, the eyes are wide open, and if a light were shone into them, the pupils would constrict. The head is covered in hair, the fingernails have reached the tips of the fingers, and the toenails are close behind. The lungs are still developing, so if born at this stage, the baby will probably need assistance breathing.