Tuberculin Skin Test Safety in Pregnancy
Yes, the tuberculin skin test (TST) is safe during pregnancy and has no adverse effects on the pregnant mother or fetus. 1
Safety Evidence
The American Thoracic Society and CDC joint statement explicitly confirms that there is no evidence that the tuberculin skin test causes harm to pregnant women or their babies. 1 This conclusion is based on extensive clinical experience with TST administration during pregnancy across multiple studies. 2, 3
Key safety points:
- The TST does not cross the placental barrier in a way that causes fetal harm - it is a diagnostic skin test, not a systemic medication. 2
- No teratogenic effects have been documented with TST administration at any stage of pregnancy, including the first trimester. 3
- Pregnancy does not significantly alter TST interpretation - the standard classification scheme (≥5 mm for high-risk, ≥10 mm for moderate-risk, ≥15 mm for low-risk individuals) remains valid during pregnancy. 2, 3
When to Perform TST in Pregnancy
Pregnant women should be targeted for tuberculin skin testing only if they have specific risk factors for latent TB infection (LTBI) or for progression to active disease. 1 Universal screening is not recommended. 3
Specific risk factors include:
- Recent exposure to active TB cases 3
- HIV infection 3
- Immigration from high TB-burden countries 4
- Healthcare workers with TB exposure 2
- Immunosuppressive conditions 5
Test Performance Considerations
While the TST is safe, pregnancy may affect test sensitivity, particularly at delivery. 6 Research shows that TST positivity rates may be lower during pregnancy compared to postpartum (11-17% vs 25%), suggesting some immunologic suppression. 6 However, this does not affect the safety of performing the test - only its diagnostic accuracy. 6
Alternative testing: Interferon-gamma release assays (IGRAs) like QuantiFERON may have better diagnostic yield than TST during pregnancy (32% vs 12% positivity), though both tests are safe to perform. 7, 8
Follow-Up After Positive TST
If a pregnant woman tests positive, a chest radiograph with appropriate abdominal shielding should be performed immediately to exclude active TB, even during the first trimester. 3 The risk of undiagnosed active TB far outweighs the minimal radiation exposure with proper shielding. 3
Common Pitfall to Avoid
Do not delay TST testing in pregnant women with TB risk factors based on unfounded safety concerns. 2, 3 The test itself poses no risk, and identifying TB infection or disease during pregnancy is critical for maternal and fetal health. 1, 5 Untreated active TB during pregnancy carries significant morbidity and mortality risks that far exceed any theoretical concerns about diagnostic testing. 5