Background: Restless legs syndrome (RLS) is the most common movement disorder in pregnancy, which can be idiopathic or secondary. There are limited comparative data regarding these two forms of RLS. The aim of this study was to compare clinical features of idiopathic and secondary RLS in pregnant women.Methods: Over a period of 3 months, 443 women who admitted for delivery in two clinical centers were screened for RLS using four diagnostic criteria of the international RLS study group. A total of 79 subjects diagnosed with RLS were consecutively enrolled in the present study. All of them were interviewed for medical history and complaints during pregnancy and responded to self-administer international RLS rating scale.Results: Ten subjects (12.9%) out of 79 pregnant women with RLS had idiopathic form, and their mean age was significantly higher than patients with secondary RLS (30.6 ± 7.3 years vs. 26.4 ± 4.6 years, P = 0.0260). Compared with women with secondary RLS, sl ep duration in pregnancy was significantly decreased in idiopathic RLS group (P = 0.0460), whereas RLS severity score was similar in both groups. No significant difference was observed between the two groups in terms of other sleep complaints, the positive family history of RLS, parity, duration of pregnancy, or frequency of cesarean section (P > 0.0500).Conclusion: Idiopathic and secondary RLS have relatively similar courses and features during pregnancy. However, the idiopathic form may have more negative impact on sleep in pregnancy. Careful screening and effective treatment of idiopathic RLS before pregnancy is recommended to limit these disturbances.