Introduction: The incidence of thyroid dysfunction in pregnancy in the western literature is suggestive of hyperthyroidism as 1:500 and hypothyroidism as 1:100. There are no proper studies in India which give us the reference figures. Several studies have found thyroid dysfunction including subclinical hypothyroidism are associated with adverse pregnancy outcomes. Because of these studies, some organizations have recommended routine prenatal screening for subclinical hypothyroidism by doing TSH for all pregnant women. In our country where we have a higher prevalence of iodine deficiency; it is expected that the prevalence of subclinical cases would also be higher. We hope to establish the reference levels for thyroid hormones in Indian pregnant subjects in correlation to their clinical profile. Methods: A prospective observational study was carried out at a tertiary care hospital in Pune, India for 02 years, among 500 pregnant ladies attending ANC OPD. A venous sample was drawn from all women, once in each trimester. All samples were assessed for alteration of TSH, FT4 and FT3. Results: The overall thyroid dysfunction cases is 12.6%, out of which 5.8% are subclinical hypothyroid, 3.8% subclinical hyperthyroid, 2.6% overt hyperthypothyroid and 0.4% are overt hyperthyroid. Conclusion: There is high burden of thyroid diseases in India. It affects women of reproductive age group. There is a paucity of data on the epidemiology of thyroid diseases. Aggressive case finding in pregnant woman at risk for thyroid diseases needs to be emphasized. While assessing and interpreting the thyroid status of the pregnant women we need to keep the trimester specific ranges in mind.