Clinical Significance
TSH, Pregnancy - TSH levels are lower during pregnancy, especially during the 1st trimester. Based on recent clinical studies which have shown that even mildly elevated TSH during pregnancy is associated with adverse pregnancy outcomes, the American Thyroid Association has released clinical guidelines which recommend the use of assay-specific and trimester-specific reference intervals.

Preferred Specimen(s)
1 mL serum

Minimum Volume
0.7 mL

Transport Container
Serum Separator Tube (SST®)

Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days

Patient Preparation
Specimen collection after fluorescein dye angiography should be delayed for at least 3 days. For patients on hemodialysis, specimen collection should be delayed for 2 weeks.
According to the assay manufacturer Siemens: "Samples containing fluorescein can produce falsely depressed values when tested with the Advia Centaur TSH3 Ultra assay."

Methodology
Immunoassay (IA)

Reference Range(s)
First Trimester    0.26-2.66 mIU/L
Second Trimester    0.55-2.73 mIU/L
Third Trimester    0.43-2.91 mIU/LResults are flagged based on the first trimester assay-specific reference interval. For later stages of pregnancy, interpret results based on the trimester-specific reference intervals provided.

Alternative Name(s)
Pregnancy TSH