This trial will be a multi-center, double blind, placebo-controlled, randomized clinical trial. All mothers identified with prolonged rupture of membranes and/or oligohydramnios, and all inborn infants < 30 weeks gestational age (GA) at birth will be screened for enrollment. Infants who meet all inclusion and exclusion criteria within the first 48 hours after birth will be randomized to either inhaled NO starting at 20 ppm, or matched placebo, delivered by means of a blinded INOvent® delivery device. Randomization will be stratified by center and treatment will be assigned using an interactive voice or web-based response system (IVRS). All infants will receive up to 14 days of therapy, following a dose reduction schedule. The primary outcome measure will be change in oxygenation at 1 hour after start of therapy. In order to determine the effects of iNO therapy on survival and need for mechanical ventilation, cross-over will not be allowed.