In a prospective study of 247 pregnant Chinese women, the prevalence of sleep disturbances across pregnancy has been assessed using a set of validated questionnaires including the Sleep and Health Questionnaire (SHQ) and the Epworth Sleepiness Scale (ESS). The frequency of self-reported snoring increased from 29.7% in the first trimester to 40.5% and 46.2% in the second and third trimesters, respectively, with an increase in the prevalence of moderate or severe snoring from 1% in the first trimester to 7.2% in the third trimester (P < 0.01). There was a higher frequency of moderate to severe snoring intensity among subjects with BMI >or=25 compared with those with BMI <25 kg/m(2) in the third trimester (20.8%vs 5.3%, P < 0.01). Subjective sleepiness, as determined by the ESS, increased significantly from 8.6 to 9.4 and 9.6 in the first, second and third trimesters, respectively.