RLS is the most extensively studied sleep disorder in pregnancy. RLS may be primary/idiopathic or secondary to a medical condition. Primary RLS occurs sporadically or by autosomal dominant inheritance. Secondary causes of RLS include pregnancy, iron deficiency, uremia, peripheral neuropathy, and medications (e.g. antihistamines, antidepressants, and dopamine antagonists). RLS should be differentiated from nocturnal leg cramps, arthritic pain, positional discomfort/paresthesias, and unconscious foot movements (e.g. foot tapping). RLS is characterized by a compelling urge to move more often than these other conditions.