The Impact of Thyroid Function and TPOAb in the First Trimester on Pregnancy Outcomes: A Retrospective Study in Peking.

CONTEXT: The impact of mild TSH elevation (2.5-4.08 mIU/L) on pregnancy outcomes is unclear. The treatment strategy for mild TSH elevation is dependent on thyroid peroxidase antibody (TPOAb) status according to the guidelines.

OBJECTIVE: To assess the effects of mild thyroid dysfunction combined with TPOAb status in the first trimester on pregnancy outcomes and the impact of levothyroxine (L-T4) treatment on pregnancy outcomes.

DESIGN: The study retrospectively evaluated 3562 pregnant women. A total of 3296 untreated women were divided into 4 subgroups: group A: 4.08 < TSH <10 mIU/L, TPOAb+/-; group B: 2.5 < TSH ≤ 4.08 mIU/L, TPOAb+; group C: 2.5 < TSH ≤ 4.08 mIU/L, TPOAb-; and group D: 0.23 ≤ TSH ≤ 2.5 mIU/L, TPOAb+/-. The other 266 women with L-T4 treatment were divided into TSH 4.08 to 10 mIU/L and 2.5 to 4.08 mIU/L subgroups.

SETTING: The study was conducted at Peking University First Hospital in China.

PATIENTS: A total of 3562 pregnant women were evaluated.

MAIN OUTCOME MEASURES: The incidence of pregnancy outcomes in the untreated subgroups (groups A-D) and treated subgroups were measured.

RESULTS: Miscarriage and maternal composite outcome risks were 3.53 (1.85-6.75) and 2.19 (1.26-3.81) times greater in group A; 1.58 (1.17-2.13) and 1.27 (1.04-1.54) times greater in group C than in group D. L-T4 improved the miscarriage risk in the TSH 4.08 to 10 and 2.5 to 4.08 mIU/L groups but doubled the risk of gestational diabetes mellitus in the TSH 2.5 to 4.08 mIU/L treated group compared with the untreated group.

CONCLUSIONS: TSH 2.5 to 4.08 mIU/L combined with TPOAb- during early pregnancy was associated with miscarriages and maternal composite outcomes. The advantages and disadvantages of L-T4 administration in TSH 2.5 to 4.08 mIU/L pregnant women remain uncertain.