According to the Endocrine Society, TSH levels should be maintained between 0.2-<2.5 mU/L in the first trimester of pregnancy and between 0.3-3 mU/L in the remaining trimesters. However, a mildly elevated TSH concentration (2.5–4.0 mIU/L) during the first trimester of pregnancy in TPOAb-negative women was not associated with adverse pregnancy outcomes in a study population. Women with a TSH between 4.5-10 mU/L or TSH greater than 10 mU/L had an increased risk of miscarriage of 1.8 or 3.95 times respectively, compared to women who had a normal TSH (0.2-2.5mU/L) during early pregnancy. Women with a TSH between 2.51-4.5mU/L did not appear to have an increased risk of miscarriage. Therefore, it is important to maintain TSH levels within the recommended range during pregnancy to avoid negative pregnancy outcomes. Women at high risk for thyroid disease should have their TSH checked as soon as pregnancy is confirmed, and women with established hypothyroidism should have their TSH tested as soon as pregnancy is confirmed and should immediately increase their levothyroxine dose.