Thyroglobulin antibodies in women with recurrent pregnancy loss: a systematic review and meta-analysis

Background: Thyroid autoimmunity is the most prevalent autoimmune disorder among women of reproductive age and has been suggested as a risk factor in recurrent pregnancy loss (RPL)-a condition in which couples suffer several consecutive pregnancy losses, but where a cause can be identified in less than half of the cases. Most studies have focused on thyroid peroxidase antibodies (TPOAbs), not considering the presence of thyroglobulin antibodies (TgAbs). The aim of this study was to systematically assess the prevalence of TgAb positivity in women with RPL, and whether TgAb positivity was associated with the outcome of the next pregnancy. Methods: A systematic literature search of PubMed and Embase (from inception to April 29, 2023) was performed for studies reporting on TgAbs in women with RPL. The primary outcome was TgAb positivity in women with RPL compared with women without RPL, with a secondary outcome of association between TgAb positivity and the outcome of the next pregnancy. Pooled effect estimates were expressed as odds ratios (ORs) with confidence intervals [CI] using a random-effects model. The study was registered with PROSPERO (No. CRD42022310232) and adhered to the PRISMA guidelines. Results: A total of 770 studies were screened, 28 of which could be included reporting data from a total of 6868 women. The prevalence of TgAb positivity in women with RPL ranged from 3.6% to 28% compared with 2.4% to 29% in women without RPL. The OR for TgAb positivity was 1.93 ([CI 1.27-2.92]; I2 = 63%) compared with women without RPL, and for TgAbs and/or TPOAbs 2.66 ([CI 1.75-4.05]; I2 = 69%). Four studies reported on the outcome of the next pregnancy after antibody measurement with highly heterogeneous results (OR for pregnancy loss ranging from 0.99 in one study to 10.0 in the other study, and two studies reported no data eligible for meta-analysis). Consequently, a meta-analysis could not be performed. Conclusions: Women with RPL were significantly more often TgAb-positive than women without RPL. Although there was a lack of studies reporting prospective outcomes, the findings of this study support the significance of awareness about the strong association between RPL and thyroid autoimmunity.