Effect of Antithyroid Antibodies in the First Trimester on Pregnancy Outcomes

Abstract Background: Some women at reproductive age have positive antithyroid antibodies (ATAs). ATA includes thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb). Women with ATAs, no matter with or without thyroid dysfunction, they have a higher risk of adverse reproductive outcomes, such as infertility, miscarriage and preterm birth.Methods: This study aimed to evaluate the impact of ATAs on maturation of women reproductive system and pregnancy outcomes. And it’s a prospective study, performed in three independent centers from January 2019 to June 2020. Women were tested for TSH, free T3, free T4, total T3, total T4, TPOAb and/or TgAb. They were divided into four groups: TPOAb+TgAb+, TPOAb+TgAb-, TPOAb-TgAb+ and TPOAb-TgAb-. Descriptive statistics were obtained for all the parameters. Mean and standard deviation were used for all quantitative parameters. The continuous variables that were nonnormally distributed were compared using the Kruskal-Wallis test. The χ2 test or Fisher exact test was used to compare categorical variables.Results: A total of 3457 women undergoing TPOAb and/or TgAb testing were enrolled in this study. 13.77% and 16.85% women were positive for TPOAb and TgAb, respectively. TgAb positivity had a strong correlation with TPOAb (F=1160.568, P＜0.001). ATAs had no effect on age of menarche and menstrual cycle. Some obstetric complications occurred in both positive subjects, but TPOAb, TgAb and TSH alone or in combination cannot predict the presence of complications during pregnancy. Administration of L-T4 to pregnant women with TSH 2.5-4.94mIU/ml may reduce the risk of PROM in ATA- women. Of the women with one or two ATAs, there were no significant differences between LT4 therapy group and untreated group in other pregnancy outcomes.Conclusion: TPOAb or TgAb is probably not the main reason for poor pregnancy outcomes.