Of 825 women, 139 women (16.8%) were TPOAb positive. A total of 444 women had a pregnancy and were included in the analyses assessing possible association between TPOAb positivity and pregnancy, live birth, and pregnancy loss rates. Of these 444 women, 69 women were TPOAb positive (15.5%) and 52 women were treated with levothyroxine (75%).
Overall, 62.8% of these pregnancies were successful in carrying the baby to term (live birth rate). The live birth rate was significantly lower in TPOAb-positive women compared to TPOAb-negative women (51.3% vs. 65.2%). TSH levels was not significantly different between women with live births and women with pregnancy losses. TPOAb-positive women who were treated with levothyroxine had a higher birth rate compared to TPOAbpositive women who were not treated with levothyroxine (61.5% vs. 29.4%). TPOAb-negative women who were treated with levothyroxine also had a higher birth rate compared to TPOAb-negative women who were not treated with levothyroxine (85.7% vs. 64.3%), but the difference was not significant.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Among women with recurrent pregnancy losses, TPOAbpositive women had a lower birth rate compared to TPOAb-negative women. Treatment with levothyroxine improved birth rate in these women. Positive TPOAb titer may be an indicator for a problem with underlying immune system, interfering with developing baby. It may also be an indicator for mild abnormalities in thyroid function, increasing the risk of pregnancy losses. Previous clinical trials have not shown clear benefit of treatment with levothyroxine in women with positive TPOAb levels, normal thyroid function, and history of infertility or pregnancy loss. However, this study looked at women in a higher risk group, with history of recurrent pregnancy losses. Doses of levothyroxine used in this study were also higher compared to doses of levothyroxine used in previous clinical trials.
Given the findings of this study, treatment with levothyroxine may decrease risk of further pregnancy loss in high-risk women with recurrent pregnancy losses. However, treatment may not be generally necessary for pregnant women with positive TPOAb titer and normal thyroid function. More studies in high-risk women are needed to confirm the benefit of levothyroxine treatment in this group.
— Sun Lee, MD