Prevalence of subclinical hypothyroidism in women with recurrent pregnancy loss and its association with autoimmune markers

Abstract

Background: Recurrent pregnancy loss (RPL), which is defined as two or more consecutive pregnancy losses experienced prior to 20 weeks of pregnancy, causes women all over the world to experience some at least 1-5% pregnancies. Subclinical hypothyroidism (SCH), thyroid autoimmunity has been proposed to be some of the factors contributing to RPL especially in areas where routine thyroid screening when receiving reproductive care is not common.

Objective: The objective of this study was to identify the frequency of SCH in women with the RPL, compare thyroid and autoimmune marker levels between RPL and the control group and determine the relationship between SCH and thyroid autoantibodies and RPL risk.

Methods: It was a three-tier case-control study carried out in three-tier hospitals in India that included 150 women with RPL and 150 matched controls aged and with a BMI of 18 years and above, who had at least one pregnancy that resulted in at least one successful birth. Blood samples were studied in terms of thyroid-stimulating hormone (TSH), free thyroxine (fT4), thyroid peroxidase antibodies (TPO-Ab), thyroglobulin antibodies (Tg-Ab), antinuclear antibodies (ANA) and anti-double-stranded DNA antibodies. A SCH was considered to be TSH higher than 4.0 mIU/L and normal fT4 levels.

Results: The SCH prevalence was also much greater in the RPL group as compared to that of controls (34.0% vs. 9.3%; p<0.001). TPO-Ab positivity was also more common among RPL cases (41.3% vs. 12.0%; p<0.001). The comorbidity of SCH and TPO-Ab positivity greatly correlated with RPL (OR 6.94; 95% CI: 3.8212.62). ANA positivity was higher in RPL women (22.0% vs. 8.0%; p<0.001). SCH was found as an independent predictor of RPL because of logistic regression with the OR 4.82 and TPO-Ab positivity (OR 3.47).

Conclusion: RPL is profoundly connected with SCH and thyroid autoimmunity. Regular thyroid and autoimmune screening in RPL screening can be used to determine the risk factors that can be modified and lead to better pregnancy outcomes.