If a woman is diagnosed with active TB during her pregnancy, will the fetus be infected? Should the baby be immunized with BCG immediately after birth?

T.S.

Tuberculosis (TB) is not a particularly difficult problem during pregnancy. The illness does not seem to be more serious when it occurs in pregnant women, and infection of the fetus seems to be quite rare. Fetal infection would occur only if there was serious widespread TB in the mother, a condition not typical in pulmonary (lung) tuberculosis.

Treatment in the non-pregnant patient involves taking three or four medications for six to nine months. Most of these medications are safe in pregnancy. Streptomycin, an antibiotic that was used quite commonly in the past, should not be given during pregnancy because it may cause ototoxicity (loss of hearing) in the fetus. Pyrazinamide, another drug commonly used to treat TB, is often avoided in pregnant patients because there are few studies looking at its effect on the fetus.

One very important consideration is the possibility that the mother will infect her baby after it is born. If the mother is still infectious when she delivers, the newborn baby could become ill. TB in an infant can be quite serious, resulting in widespread infection and death. If an infant or young child is exposed to someone with active tuberculosis, an antibiotic called isoniazid (INH) should be given to the child to prevent the development of active tuberculosis.

In some countries, typically the developing nations, vaccination against TB is routinely attempted. The only available vaccine, called BCG (for "bacillus Calmette-Guerin"), consists of a weakened strain of Mycobacterium bovis, a close relative of the bacterium that causes TB. While the vaccine is not very effective in preventing the usual pulmonary form of tuberculosis, it is very effective in preventing severe, widespread disease in children. Since this is rare in the United States, BCG is not usually given here.

In the case you describe, the BCG vaccine may be helpful if the mother is still contagious and if isoniazid cannot be given to the infant (because the child has liver problems, for example). Also, if the mother's TB was resistant to many antibiotics (so-called "multi-drug resistant TB"), then BCG should definitely be given to the infant. Aside from these instances, the vaccine is generally not necessary.