*4.3.1 Definition and epidemiology*

Restless legs syndrome (RLS) or Willis-Ekbom disease is a motor-sensory disorder of the lower limbs associated with increased likelihood of sleep–wake disorders, such as poor sleep, poor daytime function and excessive daytime sleepiness in pregnancy. This condition is almost twice as common in women as in men, but reasons for this imbalance in prevalence are not precisely understood [76]. Indeed, the first known epidemiological study of RLS during pregnancy reported a prevalence of 11.3%, but in the third trimester prevalence appeared to rise up to 30%. Pregnancy is a cause of a transitory form of the syndrome, but after several pregnancies it can also become persistent [10].
