Background: Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) related cardiovascular and metabolic risk factors such as hypertension, diabetes mellitus and dyslipidaemia which together are commonly known as metabolic syndrome (MS) is often overlooked in pregnancy. OSAHS is known to cause higher maternal morbidity and bad foetal outcome. Aim was to study the prevalence of components of MS among third trimester pregnant women with OSAHS.Methods: A total of 100 cases and 100 controls each amongst third trimester pregnant females admitted in the Department of Obstetrics and Gynecology at the Government Medical College, Kozhikode, Kerala, India were enrolled in the study. All subjects underwent a thorough clinical, anthropometric, obstetrical examination and biochemical tests such as complete blood count, blood sugar and lipid profile. The parameters were compared between cases and controls.Results: OSAHS positive pregnant women had a higher prevalence of elevated systolic (P=0.01) and diastolic (P=0.002) blood pressure, abnormal fasting (P<0.0001) and post prandial (P=0.02) blood sugar, abnormal cholesterol (P=0.006) and triglyceride levels (P<0.001), and abnormally low HDL levels (P<0.001).Conclusions: This study showed that metabolic syndrome was highly prevalent among OSAHS positive third trimester pregnancy (52%) versus OSAHS negative (8%) pregnant women.