Abstract： Aim To explore the effect of serum free triiodothyronine(FT3)/FT4 in early pregnancy on maternal and infant outcomes in patients with gestational hypothyroidism(hypothyroidism).Methods 122 pregnant women with hypothyroidism were selected as the hypothyroidism group,and 150 healthy pregnant women who underwent prenatal examinations during the same period were selected as the healthy group.The hypothyroidism group was divided into a good outcome group and a poor outcome group based on maternal and infant outcomes.The serum FT3,FT4,and FT3/FT4 levels in each group were compared.Logistic multiple regres-sion analysis was used to analyze the influencing factors on maternal and infant outcomes.ROC was used to evaluate the predictive value of FT3,FT4,and FT3/FT4 on maternal and infant outcomes.Results The serum levels of FT3,FT4,and FT3/FT4 in the hypothyroidism group were lower than those in the healthy group,while those in the poor outcome group were lower than those in the good outcome group(P＜0.05).BMI,history of miscarriage,FT3,FT4,and FT3/FT4 are risk factors for adverse maternal and in-fant outcomes in pregnant women with hypothyroidism(P＜0.05).The efficacy of FT3/FT4 in predicting maternal and infant outcomes in pregnant women with hypothyroidism was higher than that of FT3 and FT4(P＜0.05).Conclusion FT3/FT4 have good predictive value for maternal and infant outcomes in pregnant women with hypothyroidism,and have guiding significance for clini-cal diagnosis and treatment.