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.