Short-term Adverse Pregnancy Outcomes in Women with Subclinical Hypothyroidism: A Comparative Approach of Iranian and American Guidelines

Introduction: Subclinical hypothyroidism during pregnancy can be associated with numerous adverse outcomes. The purpose of this study was to compare short-term adverse pregnancy outcomes in treated vs. nontreated patients who fall within the numerical range of TSH between the reference ranges of Iranian vs. American thyroid guidelines.Materials & Methods: 80 pregnant women with TSH levels of 2.5-3.9 in the first trimester and 3-4.1 in the second and third trimesters were enrolled in the study and randomly divided into two groups including 41 patients in the intervention group and 39 in the control group. The intervention group treated with levothyroxine at least 50 µg/day and the control group received no treatment. The data was analyzed using statistical tests of frequency, mean, chi-square, t-test and SPSS v25.Results: There was no significant difference between two study groups regarding the adverse pregnancy outcomes including pregnancy loss, preterm delivery and premature rupture of the membrane (p> 0.05). The only significant finding was a correlation between pregnancy loss frequency and TPO antibody level (p=0.011).Conclusion: The results showed that untreated pregnant women with subclinical hypothyroidism who were in the intermediate range of reference either in Iranian or American guidelines did not show any significant difference in adverse pregnancy outcomes, and use of the Iranian reference range can be extended to Zanjan province population.