For ETT diameter: 2.5 mm (the smallest) for infants < 1000 g or < 28 weeks gestation 3 mm for infants 1000 to 2000 g or 28 to 34 weeks gestation 3.5 mm for infants > 2000 g or > 34 weeks gestation Intubation is safer if oxygen is insufflated into the infant's airway during the procedure.