Restless legs syndrome (RLS) is a neurosensory disorder that typically begins in the evening and often prevents a person from falling asleep. It has been associated with iron deficiency anemia and dopaminergic pathways and is often treated with iron infusion or dopamine agonists. The purpose of this secondary analysis of longitudinal data collected on women before, during, and after pregnancy is to document the prevalence of RLS during pregnancy, contrast its effect on sleep and mood state, and explore the role of folate and iron in the expression of RLS, specifically during the third trimester when the syndrome is most distressing. The prevalence increased from 0 during preconception to 23% (n = 7) during the third trimester of pregnancy. Only 1 subject continued to experience RLS after delivery. Compared with those without complaints of restless legs, those with restless legs had low serum ferritin at preconception and significantly lower folate levels during preconception and at each trimester. In addition, time to sleep onset was significantly delayed and depressed mood was significantly higher in the RLS group. Rather than indicators of iron deficiency anemia (serum ferritin, serum iron, and hemoglobin) or pernicious anemia (vitamin B(12)), it was reduced serum folate level that was associated with RLS in this sample of pregnant women. Findings indicate a need to reconsider recommendations about the normal ranges of serum ferritin and serum folate levels during pregnancy to minimize the complaints of restless legs and promote more consolidated sleep and better daytime mood state during pregnancy.