Objective To study influences of intervention in pregnant women with positive thyroid autoantibodies on the thyroid function of babies. Methods A total of 55 pregnant women were enrolled with positive thyroid peroxidase antibody (TPOAb) and/or thyroglobulin antibody (TgAb) during prenatal checkup. They were randomly divided into two groups: intervening group( n= 36, newborn group A) was treated with levothyroxine ( L-T4 ), and non-intervening group ( n= 19, newborn group B) was not treated. 30 cases of pregnant women with negative thyroid autoantibodies served as a normal population control group (newborn group N). Serum TSH, TPOAb, TgAb, TT3, TT4, FT3 and FT4 were measured by high-sensitive immunochemiluminescent assay ,and urinary iodine was also examined in the pregnant women. Fetal plasma TSH, TT3, TT4, FT3, and FT4 levels were measured after cutting the umbilical cord from placenta, and repeated measurements were made by 3-4 weeks and 8-10 weeks postpartum. Results At baseline, serum TSH levels of the pregnant women in intervening and nonintervening groups were significantly higher than that in control group ( P＜0.05 ). Non-intervening group had higher TSH and lower TT3, TT4, FT4 compared with the other two groups (P＜0. 05 or P＜0.01 ). The cord blood TSH levels of the neonates in both group B [(7.06 ± 1.31 ) mIU/L] and group A [(6.23 ± 1.26 ) mIU/L] were significantly higher than that of group N [(5.48±1. 17) mIU/L, P＜0.01 and 0. 05]. By 3-4 weeks postpartum,the serum TSH level [(3.21±0.70)mIU/L] in group B was significantly higher than those in group N [(2.72±0.51)mIU/L] and group A [(2.78±0.42) mIU/L, all P＜0.05]. The serum TSH level in group B [(2.99±0.57) mIU/L] was still higher than those in group N [(2.48±0.68) mIU/L] by 8 to 10 weeks postpartum (P＜0.05 ). Multiple stepwise regression analysis revealed that TSH, TPOAb, and urine iodine levels of mothers were independently related to TSH of their infants. Conclusion When differences in thyroid function exist in pregnant women, these differences also reside in their offspring. The thyroid function in neonates correlates with both the thyroid autoantibodies and thyroid function of their mothers.