The question of receiving a tuberculosis (TB) shot during pregnancy refers to the Bacille Calmette-Guérin (BCG) vaccine, which is used to prevent the disease. This vaccine is routinely administered to infants and children in many parts of the world where TB is common, though it is rarely recommended in countries with low TB rates, such as the United States. BCG is classified as a live-attenuated vaccine, meaning it contains a weakened, but still living, form of the Mycobacterium bovis bacterium. The nature of this live component raises specific safety concerns regarding its use in pregnant individuals.
Official Recommendations for BCG Vaccination During Pregnancy
The BCG vaccine is generally not recommended for use during pregnancy. This advisory is based on the fact that it is a live-attenuated vaccine, which carries a theoretical risk of causing a disseminated infection in the developing fetus. While major health organizations, including the Centers for Disease Control and Prevention (CDC), state that no harmful effects on the fetus have been definitively observed, the vaccine is still contraindicated as a precaution. The lack of extensive studies proving its safety in this specific population means that the theoretical risk is enough to warrant avoidance.
In the majority of countries, the low incidence of TB makes the theoretical risk unnecessary, and vaccination is simply deferred until after delivery. However, the decision becomes more complex in high-endemicity regions or in cases of unavoidable, high-risk exposure. In these extremely rare situations, an infectious disease specialist must carefully weigh the benefit of maternal protection against the theoretical fetal risk. The BCG vaccine is primarily intended to protect infants and young children from severe forms of TB, such as miliary TB and meningitis, not necessarily to prevent pulmonary TB in adults.
If a pregnant individual is inadvertently vaccinated with BCG, termination of pregnancy is not indicated, as the risk is considered hypothetical. Women who receive the BCG vaccine should be advised to avoid pregnancy for a specified period after vaccination. The standard guideline is to wait until after the woman has delivered to receive the vaccine.
Evaluating Tuberculosis Exposure Risk
A pregnant individual must first be evaluated for their risk of exposure to the TB bacterium, Mycobacterium tuberculosis. Targeted testing is recommended for those with specific risk factors, such as recent travel to or birth in a country with a high prevalence of TB. Close, prolonged contact with someone who has been diagnosed with active TB disease is another factor that warrants immediate screening.
Other risk factors include having a weakened immune system due to conditions like HIV infection or the use of immunosuppressive medications. Working in high-risk occupational settings, such as healthcare, correctional facilities, or homeless shelters, may also increase the need for testing. These assessments are conducted to determine if a person has been infected, not if they should be vaccinated.
There are two primary methods for testing for TB infection: the Tuberculin Skin Test (TST) and the Interferon-Gamma Release Assay (IGRA), which is a blood test. Both the TST and the IGRA are considered safe to use throughout all trimesters of pregnancy. The IGRA is often preferred for individuals who have previously received the BCG vaccine, as the vaccine can cause a false-positive result on the TST.
Managing Latent and Active TB Infection in Pregnancy
If testing indicates the presence of the TB bacterium, the next step is to determine whether the infection is latent or active. Latent TB Infection (LTBI) means the bacteria are dormant, causing no symptoms and not contagious. Active TB Disease is an illness that is contagious and causes symptoms. Active TB disease in a pregnant individual poses a significant hazard to both the mother and the fetus, with risks including low birth weight and congenital TB.
A diagnosis of Active TB Disease requires immediate treatment, even during the first trimester of pregnancy, due to the severe risks associated with untreated disease. The standard treatment regimen involves a combination of anti-TB drugs, specifically isoniazid, rifampin, and ethambutol, which are considered safe for use during pregnancy. Pyrazinamide is typically included in the regimen, though its use in pregnant women in the United States is sometimes reserved for severe or drug-resistant cases.
Treatment for LTBI is often delayed until two to three months after delivery to reduce the potential for drug-related liver toxicity, which is thought to be slightly higher during pregnancy. However, treatment should proceed immediately for pregnant individuals at a high risk of progression to active disease, such as those with HIV infection or a recent close exposure. Any pregnant person taking isoniazid must also take a daily Pyridoxine (Vitamin B6) supplement, usually 25–50 mg, to mitigate the drug’s possible adverse effects on the nervous system.