Women with positive antithyroperoxidase antibodies and normal thyroid function undergoing in vitro fertilization and embryo transfer (IVF-ET) treated with levothyroxine may not experience a difference in miscarriage rates or live births compared with women not treated with levothyroxine, according to a study published in JAMA.
Researchers identified a total of 600 women who had tested positive for antithyroperoxidase antibodies with normal thyroid function currently undergoing treatment for infertility in China and randomly assigned them 1:1 in an open-label trial to receive (intervention group) or not receive (control group) levothyroxine.
The purpose of the study was to assess whether treatment with levothyroxine initiated before IVF-ET would improve the live-birth rate and decrease the miscarriage rate in women who had tested positive for antithyroperoxidase but had normal thyroid function.
The primary outcome was to assess the overall miscarriage rate (loss of pregnancy before 28 weeks gestation). The secondary outcomes were to assess the clinical intrauterine pregnancy rate and live-birth rate in both groups.
According to the study results, the miscarriage rate in women treated with levothyroxine was 10.3% and 10.6% in the control group over a total of 4.5 years (rate difference [RD] –0.34%; 95% CI, –8.65% to 8.12%), and the intrauterine pregnancy rate was 35.7% and 37.7%, respectively (RD –2.00%; 95% CI, –9.65% to 5.69%).
While not a primary or secondary outcome studied, it was interesting to note the preterm delivery rate for live births was 22.1% in women treated with levothyroxine and 19.6% in women in the control group (RD 2.52%; 95% CI, –8.98% to 13.99%).
Limitations of this study included it being an open-label study, with a single population including only women of Chinese descent at a single healthcare center.
Researchers concluded that treatment with levothyroxine in women who had tested positive for antithyroperoxidase with normal thyroid function was not found to reduce the miscarriage rate or improve the live-birth rate when compared with women not treated with levothyroxine, which is normal practice. In addition, there were no significant findings or beneficial effects in all of the subgroup analysis performed in this study.
Wang H, Gao H, Chi H, et al. Effect of levothyroxine on miscarriage among women with normal thyroid function and thyroid autoimmunity undergoing in vitro fertilization and embryo transfer. JAMA. 2017;318:2190-2198.