A male infant is born at 39 weeks’ gestational age via repeat cesarean delivery to a 36-year-old (gravida 3, para 2, term 2, living 2) woman. The prenatal history is notable for group B Streptococcus– positive maternal status; the prenatal course is otherwise benign and there is no known family history of medical disorders. The infant is vigorous at birth, with spontaneous respirations and a heart rate greater than 100 beats/min; his Apgar scores are 8 and 9 at 1 and 5 minutes, respectively. He weighs 3,460 g (59th percentile), his head circumference is 34.5 cm (51st percentile), and length is 48.9 cm (30th percentile). The rest of his physical examination findings are normal. The infant initially remains with his mother; however, at approximately 15 minutes of age during skin-to-skin contact with his mother, the infant is noted to be pale, with a preductal pulse oximetry oxygen saturation of 50% in room air. He is provided continuous positive airway pressure via mask for 5 minutes, then placed on blow-by oxygen supplementation and monitored in the nursery. He has no signs of respiratory distress and is able to wean to room air after 45 minutes, maintaining pulse oximetry saturations over 90% without supplemental oxygen. Within the next hour, however, he again has desaturations on pulse oximetry and requires 1 L/min supplemental oxygen via nasal cannula. Chest radiography demonstrates mild hazy opacification of the lungs bilaterally, suspected to be retained fluid in the setting of cesarean section. His complete blood cell count and immature-to-total neutrophil ratio are normal; a blood culture specimen is obtained. At that time, the decision is made to …