Estimation and interpretation of thyroid function tests in pregnant women is of outmost importance for maternal, fetal and neonatal health. Our objective was to calculate laboratory and geography-specific reference intervals for TSH during first, second and third trimester of pregnancy in the pregnant females in District Charsadda. Fulfillment of extensive questionnaires and estimation thyroid-stimulating hormone (TSH) were performed. The reference population was defined using inclusion criteria regarding different demographic characteristics, socioeconomic conditions and general medical status of women. Reference interval for TSH was 0.2 µ IU/ml-2.02 µ IU/ml for the first trimester 0.2 µ IU/ml-1.84 µ IU/ml for the second trimester 0.56 µ IU/ml-3.09µ IU/ml for third trimester had TSH lower than the upper reference limit. These trimester-specific Population based reference ranges are essential in everyday clinical practice for the correct interpretation of thyroid hormone values and accurate classification of thyroid disorders.

Keywords: Thyroid Stimulating Hormone (TSH), Pregnancy, trimester, Fluctuation, Thyroid Function Test, socioeconomic, hormone.