Background & Objectives : Thyroid disorders are one of the commonest world over, but often under diagnosed. Hypothyroidism affects pregnancy. Khammam district ground water is deficient of iodine and hypothyroidism cases are more common here. Considering this fact, present study was undertaken to find out the relationship between Hypothyroidism and premature delivery in pregnant women attending gynaecology. and Obst. dept. of Mamata medical college Khammam. Methods : 20 cases and 20 controls of same gestational period were selected.. Serum T3, T4, TSH, FT3, and FT4 were estimated in both cases and control groups respectively. Results : The serum T3, T4, FT3, and FT4 all were decreased in cases than controls (p = 0.0000001) respectively. It is statistically highly significant. The TSH was increased in cases than controls (p = 0.0000001). It is statistically highly significant. Interpretation & conclusion :Decreased FT3, FT4, T3, T4 and elevated TSH indicate hypothyroidism and may be one of the cause of preterm delivery. Thyroid hormone estimation should routinely be done with all pregnant women, so that the proper care should be taken to avoid preterm deliveries. © 2011 Elsevier B.V., All rights reserved.