Abstract: Objective To determine the epidemiological character istics and risk factors of hypothy roidism among pregnan two men.Methods Thyroid function and urinary iodine of 2076 pregnant women and 266 women at gestational age were measured and ultrasound inspection of thyroid was conducted among the women.Results The prevalence of hypothyroidism of pregnan twomen and women at gestational age were 5 3% and 6.8%,respectively.The prevalence of hypothy roidism was 7.6% among the pregnant women with high urinary iodine,which was significantly higher than that of the adequateurinary iodine group and very high urinary iodine group(P=0.026).Positive thyroid peroxidase an tibody ratio of pregnant women in hypothy roidism group was 23.9%,which was significantly higher than those of the normal gro up(P=0.000).Multinomial lo gistic analysis showed that high urinary iodine and positive thyroid peroxidase antibody were in dependent risk factor of hypothy roidism with the oddsratio values of 221(95% confidence in te rvalCI1.36-3.60)and 4.68(95% CI 2.74-7.98),respectively.Conclusion The autoimmune thyroiditis and iodine overdose are important factors and closely associated with hypothy roidism among pregnant women.