ATA Guidelines Tools

8 Maternal Disorders Hypothyroidism and Pregnancy Î In the setting of pregnancy, maternal hypothyroidism is defined as a TSH concentration elevated beyond the upper limit of the pregnancy- specific reference range. (S-H) Î The pregnancy-specific TSH reference range should be defined as follows: • When available, population and trimester-specific reference ranges for serum TSH during pregnancy should be defined by a provider's institute / laboratory, and should represent the typical population for whom care is provided. Reference ranges should be defined in healthy, TPOAb-negative pregnant women with optimal iodine intake and without thyroid illness. (S-H) • When this is not feasible, pregnancy-specific TSH reference ranges obtained from similar patient populations, and performed using similar TSH assays should be substituted. (S-H) • If internal or transferable pregnancy-specific TSH reference ranges are not available, an upper reference limit of ~4.0 mU/l may be used. For most assays, this represents a reduction in the non-pregnant TSH upper reference limit of ~0.5 mU/L. (S-M) Î Treatment of overt hypothyroidism is recommended during pregnancy. (S-M) Î Pregnant women with TSH concentrations >2.5 mU/L should be evaluated for TPOAb status. Î Subclinical hypothyroidism in pregnancy should be approached as follows: a. LT4 therapy is recommended for: ▶ TPOAb-positive women with a TSH greater than the pregnancy specific reference range (See Thyroid Function Testing and Pregnancy Section) (S-M) ▶ TPOAb-negative women with a TSH >10.0 mU/L. (S-L) b. LT4 therapy may be considered for: ▶ TPOAb-positive women with TSH concentrations >2.5 mU/L and below the upper limit of the pregnancy specific reference range. (W-M) ▶ TPOAb-negative women TPO antibody negative women with TSH concentrations greater than the pregnancy specific reference range and below 10.0 mU/L. (W-L) c. LT4 therapy is NOT recommended for: ▶ TPOAb-negative women with a normal TSH (TSH within the pregnancy specific reference range, or <4.0 mU/L if unavailable). (S-H). Î Isolated hypothyroxinemia should NOT be routinely treated in pregnancy. (W-L)

• Cover