TB Skin Testing During Pregnancy

TB skin testing is safe during pregnancy and has no adverse effects on the pregnant mother or fetus. 1

Safety of TB Skin Testing in Pregnancy

The tuberculin skin test (TST) has been extensively studied in pregnancy and there is no evidence that it causes any harm to the pregnant woman or her unborn child 1
The current classification scheme for interpreting the Mantoux tuberculin skin test is considered valid during pregnancy, although it has not been specifically verified in pregnant women 1
Pregnancy has minimal influence on the pathogenesis of TB or the likelihood of latent TB infection (LTBI) progressing to active disease 1

While one study demonstrated a decrease in lymphocyte reactivity to tuberculin during pregnancy, other studies have not shown any effect of pregnancy on cutaneous delayed hypersensitivity to tuberculin 1
The standard interpretation criteria for TB skin testing apply during pregnancy:
- ≥5 mm induration is considered positive in high-risk individuals (HIV-positive, recent TB contacts, persons with fibrotic changes on chest radiographs) 2
- ≥10 mm induration is considered positive in moderate-risk individuals (recent arrivals from high-prevalence countries, injection drug users) 2
- ≥15 mm induration is considered positive in low-risk individuals with no known risk factors 2

Pregnant women should be targeted for tuberculin skin testing only if they have specific risk factors for LTBI or for progression of LTBI to disease 1
When TB screening is indicated during pregnancy, immune tests such as TST or Interferon Gamma Release Assays (IGRAs) should be used 3, 4
For pregnant women who are BCG-vaccinated or immunocompromised, IGRAs may be preferred over TST 3
If a pregnant woman has a positive TB skin test, a chest radiograph with appropriate shielding should be performed to exclude active TB, even during the first trimester 1

Some studies suggest that IGRA tests may be more stable during pregnancy than TST, with QGIT (QuantiFERON Gold In-tube) positivity remaining more consistent between antepartum and delivery periods compared to TST results 5
The postpartum period may show increased positivity for both TST and IGRA tests, which should be considered when interpreting results 5
In low incidence settings, concordance between TST and IGRA ranges from 77-91%, with kappa values of 0.26-0.45 6

If chest radiographs are normal and no symptoms of active TB are present, tuberculin-positive pregnant women may be candidates for treatment of LTBI 1
Treatment decisions for LTBI during pregnancy should balance the risk of isoniazid hepatotoxicity against the risk of developing active TB and its consequences for both mother and child 1
For women at high risk for progression to active TB (especially those with HIV infection or recent infection), treatment should not be delayed based on pregnancy alone 1
For women with lower risk, some experts prefer to delay treatment until after delivery 1

Failure to read the TB skin test within the recommended 48-72 hour window can lead to inaccurate results 5
Pregnancy itself does not increase the risk of progression from LTBI to active disease, but the postpartum period may be associated with increased risk of TB reactivation 6
If active TB is suspected, a more comprehensive evaluation including sputum examination should be performed before starting any treatment 1