New onset of restless legs syndrome in pregnancy in a prospective multiracial cohort

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.