Restless legs syndrome (RLS) is more common in pregnant women. The objective of our study was to determine frequency of RLS in pregnant women and predictors of RLS in pregnancy in Pakistan. All pregnant women admitted at The Aga Khan University Hospital for delivery from June to July 2005 were enrolled. Eighty-one of 271 (30%) interviewed women fulfilled the diagnostic criteria of RLS. One hundred seventeen (43%) of the subjects dropped their haemoglobin during the pregnancy. No significant difference in haemoglobin drop was noted between the RLS group and healthy group. On multivariate analysis family history of RLS (OR: 8.43, CI: 2.32-30.57, p value<0.001), history of RLS in prior pregnancy (OR: 53.74, CI: 6.72-429.8, p value<0. 001), history of RLS in past even when non-pregnant (OR: 12.91, CI: 3.34-49.87, p value<0.001) and haemoglobin of 11g/dL or less (OR: 2.05, CI: 1.04-4.04, p value 0.036) were found to be independent predictors of RLS during pregnancy. Subgroup analysis revealed that family history of RLS (OR: 3.06, CI: 1.2-7.83, p value 0.019) and anemia (OR: 1.89, CI: 0.96-3.71, p value 0.06) were associated with de novo RLS, and family history of RLS (OR: 12.39, CI: 4.45-35.54, p value<0.001) and multiparity (OR: 6.84, CI: 2.15-21.71, p value 0.001) were predictors of pre-existing RLS.