Background:
Subclinical hypothyroidism (SCH) is the most common thyroid dysfunction during pregnancy. Despite well-defined clinical guidelines on treatment of overt hypothyroid in pregnant women, there is no consensus on Levothyroxine (LT4) treatment of SCH women.Objective: In this meta-analysis we aimed to evaluate the benefits of Levothyroxine treatment on pregnancy outcomes in SCH women.Materials and Methods: PubMed [including Medline], Web of Science, Wiley, Google Scholar, Science direct and Scopus were searched for retrieving articles published in English language on effects of Levothyroxine treatment on pregnancy outcomes in pregnant women with SCH compared to untreated or healthy controls up to 2018. In this systematic and meta-analysis, both fixed and random effect models were applied to estimate pooled effect size. Heterogeneity and publication bias were evaluated using the I-squared (I2) and Begg’s statistics, respectively.Results: Twelve cohort studies and randomized controlled trials with a total of 11307 participants were analyzed. This meta-analysis showed that pregnant women with SCH treated with levothyroxine had lower chances for pregnancy loss (OR: 0.71, 95% CI: 0.57-0.88; I2=0%) and higher chances for live birth rate (OR: 2.72, 95% CI: 1.44-5.11; I2=25%) than placebo group. Compared to euthyroid women, patients with SCH treated with levothyroxine had a higher odds ratio for preterm labor (OR: 1.80, 95% CI: 1.13-2.86; I2=0%). There was not any significant difference in chances of other adverse maternal complications, obstetrical hemorrhage, and neonatal/NICU admission between patients with SCH treated with levothyroxine and control groups (placebo and euthyroid).Conclusion: This study shows that the effect of treatment with levothyroxine in pregnant women with SCH is not the same for all pregnancy outcomes. Levothyroxine treatment in these patients can reduce the loss of pregnancy. Due to the limited number of studies, further studies are needed to conclude more precisely about other consequences.