New onset of restless legs syndrome in pregnancy in a prospective multiracial cohort: Incidence and risk factors

OBJECTIVE: To determine whether the incidence and risk factors of restless legs syndrome (RLS) in pregnancy differ by race/ethnicity, we estimated relative risks of demographic, socioeconomic, and nutritional factors in association with risk of any incident RLS in pregnancy in a cohort of 2,704 healthy pregnant women without prior RLS. METHODS: Using data from the multicenter, multiracial National Institute of Child Health and Human Development (NICHD) Fetal Growth Studies-Singletons, we examined the incidence of RLS from early pregnancy to near delivery through up to 6 assessments. Multivariable Poisson models with robust variance were applied to estimate relative risks (RRs). RESULTS: The cumulative incidence of RLS in pregnancy was 18.1% for all women, 20.3% for White women, 15.4% for Black women, 17.1% for Hispanic women, and 21.1% for Asian women. Among Hispanic women, older age (RR [reference ≤25 years]: 25-35 years, 1.51; 95% confidence interval [CI] 1.05-2.16; ≥35 years, 1.58; 95% CI 0.93-2.68), anemia (RR [reference no]: yes, 2.47; 95% CI 1.31-4.64), and greater total skinfolds of the subscapular and triceps sites, independent of body mass index (RR [reference quartile 1]: quartile 5, 2.54; 95% CI 1.30-4.97; p trend = 0.01) were associated with higher risk of RLS, while multiparity was associated with a lower risk (RR [reference nulliparity]: 0.69; 95% CI 0.50-0.96). In Black women, greater skinfolds and waist circumference were associated with higher risk of pregnancy RLS, although the trends were less clear. CONCLUSIONS: The incidence of RLS in pregnancy was high and differed by race/ethnicity, which is likely accounted for by differences in other risk factors, such as age, parity, and nutritional factors.