Sixteen percent of the women who are euthyroid and positive for TPO or TG antibodies in the first trimester will develop a TSH that exceeds 4.0 mIU/L by the third trimester [38], and 33%–50% of women who are positive for TPO or TG antibody in the first trimester will develop postpartum thyroiditis [39–41]. Here, TPO is linked to thyroiditis.