 Studies of IH during the early postnatal wks of life in very preterm infants may be due to other mechanisms, including ineffective ventilation or other acute morbidities. However, H in spontaneously breathing convalescing infants is due to ventilatory immaturity with associated respiratory pauses or brief apneas, and has a characteristic pattern of brief desaturation from a normoxic baseline followed by reoxygenation and return to normoxia. This study will assess IH only during spontaneous breathing in infants after resolution of acute morbidities or need for supplemental O2, and approaching term-equivalent age, a time when IH has been shown by other studies to be the consequence of immature breathing regulation. 