Abstract: Objective: To explore the effects of abnormal thyroid function on the pregnancy outcome.Methods: Three thousand seven hundred and seventy-eight pregnant women without the history of thyroid disease were divided into the hyperthyroidism group,hypothyreosis group,subclinical hypothyreosis group,other thyroid disease group and normal control group according to the thyroid function.The processes and outcomes of pregnancy between all groups were analyzed and compared.Results: The preterm delivery rates of the hyperthyroidism group,hypothyreosis group,subclinical hypothyreosis group and low thyroid group were significantly higher than that of the normal group(P<0.01).The incidence of adverse outcome in all groups were higher than that in normal control group(P<0.01).The differences of the neonatal 5 min Apgar scores between the hyperthyroidism group,hypothyreosis group,subclinical hypothyreosis group,low thyroid group and normal control group were not statistically significant(P>0.05),the neonatal weights in hyperthyroidism group and hypothyreosis group were lower than that in normal control group(P<0.01).The differences of the occurrence rates of respiratory distress syndrome,intrauterine growth retardation,hypertensive disorder complicating pregnancy and postpartum infection between pregnant with abnormal thyroid function and normal control group were statistically significant(P<0.01).The incidence of respiratory distress syndrome in hyperthyroidism group,hypothyreosis group and subclinical hypothyreosis group,and the incidence of hypertensive disorders in hyperthyroidism group and hypothyroidism group were higher than those in normal control group(P<0.01).Conclusions: The regular testing of FT3,FT4 and thyroid stimulating hormone is very helpful to know the thyroid function of pregnant,which can induce the complications and improve the pregnancy outcome.