Factors Affecting New-Onset of Restless Legs Syndrome in Pregnancy

Researchers investigated the incidence and risk factors of restless legs syndrome in pregnancy and their relationship to race and ethnicity.

Pregnant women often develop restless legs syndrome (RLS), however the incidence of RLS in this population was associated with ethnicity, age, and nutritional factors according to study results published in Neurology.

Study researchers analyzed data from a multicenter, prospective cohort study conducted between 2009 and 2013. They recruited pregnant women (N=2704) between 8 and 13 weeks’ gestation and assessed them for symptoms of RLS during 5 follow-up visits. Participation in this study was reduced during the course of the study, from 2554 at the first follow-up to 2056 at the last.

The women were 28.1 (Standard Deviation [SD], ±5.51) years of age, 39.4 percent had a bachelor’s degree or higher degree, 25.5 percent earned less than 30,000 dollars annually, and average prepregnancy weight was 67.3 (SD, ±15.0) kg. Stratified by ethnicity, Asian women had the lowest body mass index (P <.0001) and smallest waist circumference (P <.0001), Hispanic women had the largest waist circumference (P <.0001) and total skinfold thickness (P <.0001), and Black women had the highest prepregnancy weight (P <.0001) and rate of anemia (P <.0001).

RLS was reported by 18.1 percent of women in the study. The incidence differed by ethnicity: It was more common among Asian women (21.1%), followed by White women (20.3%), Hispanic women (17.1%), and Black women (15.4%; P =.03). At 8 to 13 weeks, the incidence rate was 0.9 to 1.7 percent and increased to its peak at 24 to 29 weeks’ gestation (4.6-8.1%), decreasing to 1.2 to 2.3 percent during the final assessment at 38 to 41 weeks’ gestation.

Among all women, higher risk for RLS was associated with increased subcutaneous fat in quintiles 4 (relative risk [RR], 1.46; 95% CI, 1.11-1.93; P =.01)or 5 (RR, 1.46; 95% CI, 1.06-2.02; P =.001) and age ([25-35 years: RR, 1.32; 95% CI, 1.04-1.66; P =.02] vs [>35 years: RR, 1.41; 95% CI, 1.04-1.90; P =.03]). Lower risk was associated with multiple pregnancies (RR, 0.76; 95% CI, 0.64-0.91; P =.002).

Among Hispanic women, those with greater subcutaneous fat (quintile 4: RR, 2.19; 95% CI, 1.16-4.15; P =.02; quintile 5: RR, 2.54; 95% CI, 1.30-4.97; P =.01), anemia (RR, 2.47; 95% CI, 1.31-4.64; P =.01), or aged 25 to 35 years (RR, 1.51; 95% CI, 1.05-2.16; P =.02) were at increased risk. Hispanic women who were not in their first pregnancy (RR, 0.69; 95% CI, 0.50-0.96; P =.03) were at decreased risk.

Among Black women, those with greater subcutaneous fat (quintile 4: RR, 2.13; 95% CI, 1.20-3.77; P =.01) and waist circumference (quintile 4: RR, 2.01; 95% CI, 1.07-3.77; P =.03) were at increased risk for RLS.

This study may have been biased by the rate of RLS, which was lower than in the general population (3% vs 5%-10%, respectively). Additionally, there was only 1 question that evaluated the RLS mimic symptom, creating the possibility of false-positive RLS cases.

“RLS incidence in pregnancy differed by race/ethnicity, which were likely accounted for by differences in distributions of other risk factors, such as age, prepregnancy BMI, and parity,” concluded the study researchers, however “future studies to understand the pathophysiologic mechanisms underlying the findings are warranted.”


Na M, Wu J, Li M, Hinkle SN, Zhang C, Gao X. New onset of restless legs syndrome in pregnancy in a prospective multiracial cohort: incidence and risk factors. Neurology. 2020;95(24):e3438-e3447. doi:10.1212/WNL.0000000000011082