Abstract
Women submitted to ART treatments represent a select subgroup of individuals. Several studies have described the relationship between TAI and pregnancy outcomes as a result of ART, with contradictory results. The purpose of this systematic review was to determine the association between TAI and the risk of miscarriage in pregnancies resulting from ART. MEDLINE via PubMed, LILACS and Embase were searched for studies published in peer-reviewed journals from 1999 to 2017. The studies were summarized using the fixed effects model and the Peto's method to calculate RR in order to flesh out the association between TAI and spontaneous abortion. Only four papers were included in this systematic review and meta-analysis. Thirty-one miscarriages were observed in 210 clinical pregnancies of women with antithyroid antibodies; and 158 miscarriages were seen in 1,371 pregnancies without antithyroid antibodies. The meta-analysis failed to find an association between TAI and higher risk of reproductive loss, RR=0.94 95% confidence interval: 0.71-1.24; p=0.879. In conclusion, the presence of antithyroid antibodies was not associated with increased reproductive loss in patients submitted to ART treatments. It is our opinion that the presence of antithyroid antibodies should be considered as a secondary biomarker of autoimmune disease, rather than an actual cause of miscarriage in patients undergoing ART. Due to the small amount of evidence on the matter, the determination of TAI before the initiation of ART should be limited to research contexts.
Highlights
The percentage of women in the general population with thyroid autoimmunity (TAI), whether by thyroglobulin autoantibodies or anti-thyroid peroxidase antibodies (TPOAb), may be as high as 20% (Davies, 2016; Łukaszuk et al, 2015)
The purpose of this systematic review was to determine the association between TAI and the risk of miscarriage in pregnancies resulting from assisted reproductive technology (ART)
These findings were consistent with the results reported by Karacan et al (2013), in which implantation rates, spontaneous abortion rates, and pregnancy rates did not differ significantly between the groups with TAI and without TAI
Summary
The percentage of women in the general population with thyroid autoimmunity (TAI), whether by thyroglobulin autoantibodies (anti-Tg) or anti-thyroid peroxidase antibodies (TPOAb), may be as high as 20% (Davies, 2016; Łukaszuk et al, 2015). In 1930, Stagnaro-Green et al (1990) described the association between TAI and risk of spontaneous abortion. Other studies suggested that the presence of TAI in euthyroid women was associated with a 2-3 fold higher risk of miscarriage (Chen & Hu, 2011; Thangaratinam et al, 2011). Women submitted to assisted reproductive technology (ART) treatments represent a select subgroup of individuals. Several studies have described the relationship between TAI and pregnancy outcomes as a result of ART, with contradictory results (Abalovich et al, 2007; StagnaroGreen & Glinoer, 2004).
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