Abstract: Objective In order to reveal the effects of iodine nutrition and pituitary-thyroid function during early pregnancy.Methods To collect urine and vein blood in pregnant women(12-14 weeks)who lived in the city for more than 3 years and earned medium income.To use As(n)-Ce⁴⁺ catalytic spectrophotometry to measure urine iodine content and use A utomated Chemiluminescence System to test pituitary-thyroid hormones.Results Urine iodine(146.5μg/L)and serum iodine(82.2μg/L)of 110 early pregnant women group showed significantly lower compared with that of 115 nonpregnant group(293μg/L and 90.8μg/L,P_av<0.01).Free thyroxine(FT₄)level(15.25pmol/L)of 70 early pregnant women group were lower than the nonpregnant group(16.75pmol/L and P<0.01).FrT₃/FT₄(0.331)and thyroid stimulating hormone (TSHs,2.41mU/L)w as higher than the nonpregnant group(0.314 and 1.84mU/L,P_av<0.01).Urine iodine of early pregnant women less than 100μg/L were 14.5%,and was higher than 5.2% of nonpregnant women(P<0.05).Conclusion Iodine nutrition and pituitary-thyroid function during pregnancy(12-14 weeks)took place changes in iodine sufficient area.Iodine reser ved in body decreased in early pregnancy,FT₄ also decreased,and yet TSHs increased on the contrary.TSHs level of 3 cases(4.3%)of early pregnancy groupwent beyond clinical reference intervals.Therefore,the prevention and cure of IDD should start before pregnancy.