Pregnancy accounts for most of the gender difference in prevalence of familial RLS.

Objective: This study was designed to evaluate the associated risk of RLS with pregnancy in relation to the family history and the age of symptom onset of RLS.

Methods And Subjects: Data from a prior RLS family history study in which 1019 subjects (527 males, 492 females) were interviewed, provided a diagnosis and characterization of RLS and determination of pregnancy status on which the current study analysis was undertaken.

Results: In the family members of RLS probands, the prevalence of RLS was significantly higher for parous women than for nulliparous women (49.5% vs. 33.7%, OR=1.92, 95% CI=1.16-3.19) or for men (49.5% vs. 30.0%, OR 2.29, 1.69-3.10), but no different for nulliparous women compared to men (33.7% vs. 30.0%, OR 1.19, 0.72-1.96). When only those whose RLS started at or after age 30 were considered, similar differences occurred. These differences were not observed among family members of control probands.

Conclusions: These data indicate pregnancy has a major impact on the risk of developing RLS for those with a family history of RLS. This pregnancy effect appears to account for most of the gender differences often reported in overall RLS prevalence data.