Endocrine Abstracts

Background: Thyroid autoimmunity is the most prevalent autoimmune disorder among women of reproductive age and has been linked to pregnancy loss. In recurrent pregnancy loss (RPL), couples suffer several consecutive losses resulting in physical as well as psychological strains. Thyroid autoimmunity has been suggested as a risk factor in RPL, but most studies have focused on thyroid peroxidase antibodies (TPOAbs), not taking into account the presence of thyroglobulin antibodies (TgAbs). The aim of this study was to systematically assess the prevalence of TgAbs in women suffering from RPL, and whether TgAb-presence was associated with a lower live birth rate in the next pregnancy.

Methods: A systematic literature search for studies reporting on TgAbs in women with recurrent pregnancy loss was performed. The primary outcome was TgAb-positivity in RPL women compared to healthy controls, with a secondary outcome of association between TgAb-positivity and live birth in the next pregnancy. Pooled effect estimates were expressed as odd ratios (OR) with 95% confidence intervals (95% CI) using a random-effects approach. Heterogeneity was reported as I² statistic. The study was registered with PROSPERO and adhered to PRISMA guidelines.

Results: A total of 518 studies were screened, sixteen of which included a total of 3869 women. The prevalence of TgAb-positivity in women with RPL ranged from 3.6 to 27% compared to 2.3 to 29% in healthy controls. The OR for women with RPL being TgAb-positive was 2.21 (95% CI: 1.54-3.12; I²=36%) compared to healthy controls, while the OR for women with RPL being positive for TgAbs and/or TPOAbs was 2.23 (95% CI: 1.45 to 3.44; I²=61%). Two studies reported on the outcome of the next pregnancy after referral in TgAb-positive women compared to TgAb-negative women and yielded highly heterogenous results. One study reported an almost equal risk of pregnancy loss (OR 0.96), while the other reported an OR of 10.0 for pregnancy loss in women being TgAb-positive. Consequently, a meta-analysis could not be performed.

Conclusion: Women suffering from RPL were significantly more often TgAb-positive than healthy controls - independent of TPOAb-positivity. No conclusion could be drawn on the association of TgAbs and subsequent live birth rate in women with RPL because of high heterogeneity and an overall lack of prospective studies on the topic. Such studies are necessary in order to firmly determine the role of thyroid autoimmunity in RPL.