Tuberculin Skin Test Safety in First Week of Pregnancy
Yes, the tuberculin skin test (TST) is safe to perform during the first week of pregnancy and throughout all trimesters. There is no evidence of adverse effects on the pregnant mother or fetus from tuberculin skin testing 1.
Evidence for Safety
The American Thoracic Society/CDC joint guidelines explicitly state that "there is no evidence that the tuberculin skin test has adverse effects on the pregnant mother or fetus" 1. This safety profile extends to all stages of pregnancy, including the critical first trimester when organogenesis occurs.
The TST involves intradermal injection of purified protein derivative (PPD), which is a diagnostic test that elicits an immune response rather than introducing live organisms or teratogenic substances. Multiple studies have confirmed its safety profile throughout pregnancy 2.
Clinical Considerations
Pregnant women should only be targeted for tuberculin skin testing if they have specific risk factors for latent TB infection (LTBI) or for progression to active disease 1. Risk factors include:
- Recent close contact with active TB cases
- Immigration from high-prevalence countries
- HIV infection or other immunosuppression
- Living in high-risk congregate settings
- Healthcare workers with TB exposure
Test Performance in Pregnancy
While the TST is safe, be aware that pregnancy may affect test interpretation. Some studies suggest decreased lymphocyte reactivity to tuberculin during pregnancy, though other studies have not confirmed this effect 1. The standard interpretation criteria (≥5 mm, ≥10 mm, or ≥15 mm based on risk factors) remain valid, though they have not been specifically validated in pregnant populations 1.
TST appears more reliable than interferon-gamma release assays (IGRAs) during pregnancy, as IGRAs show decreased positivity due to reduced interferon-gamma responses during pregnancy 3. TST was less affected by pregnancy-related immune changes in comparative studies 3.
Administration Details
The test should be administered as 0.1 mL of 5 tuberculin units (TU) PPD intradermally into the forearm, and read at 48-72 hours by measuring the transverse diameter of induration in millimeters 1.