The influence of BCG immunization on tuberculin reactivity in healthy Chilean women in the third trimester of pregnancy.

SETTING: Tuberculin testing is an accepted method for screening pregnant women for tuberculosis. The interpretation of tuberculin reactivity in bacillus Calmette-Guerin (BCG)-immunized pregnant women is still in debate. OBJECTIVE: Four related issues were addressed: (1) The effect of pregnancy on tuberculin reactivity; (2) the effect of age differential on tuberculin reactivity; (3) the effect of repeated immunization with BCG; and (4) the risk of developing tuberculosis during pregnancy or a 3-year post-partum period. DESIGN: We performed tuberculin testing in 840 healthy Chilean women in the 32nd to 34th week of pregnancy; 807 had been immunized with 1 or more doses of BCG. There were 3 age groups: 177 were < or = 19 years old, 534 were 20-29 years old, and 129 were > or = 30 years old. All women in the study were followed at least 3 years post-partum. RESULTS: Women < or = 19 years old and non-pregnant women of similar age studied in the same geographical area had a similar distribution of the size of tuberculin reactions. Over 50% of all BCG-immunized women in each group had tuberculin reactions > or = 10 mm. A differential effect of different doses of BCG was significant only in 20- to 29-year-old women. None of the women in this study developed tuberculosis during pregnancy or a 3-year post-partum observation period. CONCLUSIONS: Healthy, BCG-immunized pregnant women may have positive tuberculin reactions without having an increased risk for tuberculosis. The incidence of tuberculosis and the BCG immunization status need to be considered in the development of policy recommendations for diagnosis and treatment of Mycobacterium tuberculosis infection in pregnant women.