In children, causes of obstructive sleep apnea often include enlarged tonsils or adenoids, and dental conditions such as a large overbite. Less common causes include a tumor or growth in the airway, and birth defects such as Down syndrome and Pierre-Robin syndrome. Down Syndrome causes enlargement of the tongue, adenoids and tonsils and there is decreased muscle tone in the upper airway. Pierre-Robin syndrome actually has a small lower jaw and the tongue tends to ball up and fall to the back of the throat. Although childhood obesity may cause obstructive sleep apnea, it's much less commonly associated with the condition than adult obesity.