By 25 to 26 weeks, premature babies weigh about 1 1/2 to 2 pounds, and are about 9 inches long when measured from head to bottom. Babies born at this time are called micro preemies, and they face long NICU stays and have many health issues related to prematurity.
By 26 weeks gestation, premature babies' lungs are starting to develop alveoli, the air sacs that allow gas exchange. Although they are still too young to breathe without help, this is a major milestone! Other developmental milestones for 25 and 26 weekers include the development of the startle reflex - a baby born at this time will startle at loud noises. Footprints and fingerprints are also developing.