What is the COMMONEST cause of stridor in a newborn?

Laryngomalacia is the most common cause of stridor in neonates. Stridor occurs within the first 2-4 weeks of life. In this case, stridor becomes worse with crying and agitation and is relieved by lying in the prone position. Vocal cord paralysis is the second most common cause of vocal cord paralysis. Stridor is primarily inspiratory in supraglottic disorders such as laryngomalacia. It is biphasic or inspiratory and expiratory in glottic and subglottic disorders such as vocal cord disease, subglottic stenosis. It is expiratory in tracheal disease such as tracheomalacia. Ref: Pediatric Emergency Medicine By Steven G. Rothrock PAGE 68.