A population-based case-control study of the safety of oral anti-tuberculosis drug treatment during pregnancy.

OBJECTIVE: To study the human teratogenic potential of isoniazid and other anti-tuberculosis drug treatment during pregnancy.

DESIGN AND SETTING: Cases from a large population-based dataset at the Hungarian Case-Control Surveillance of Congenital Abnormalities, and controls from the National Birth Registry, between 1980 and 1996. Information on all oral anti-tuberculosis drug treatments during pregnancy was medically recorded.

STUDY PARTICIPANTS: Women who had newborns or fetuses with congenital abnormalities (case group), and women who had babies with no congenital abnormality (control group).

MAIN OUTCOME MEASURES: Congenital abnormalities in newborn infants and fetuses diagnosed prenatally during the second and third trimesters, and postnatally from birth to the age of one year.

RESULTS: Of 38,151 controls, 29 (0.08%) were exposed to anti-tuberculosis drug treatment during pregnancy; the corresponding figures for cases were 22,865 and 11 (0.05%). The prevalence odds ratio was 0.6 (95%CI 0.3-1.3). Analysis of isoniazid and other oral antituberculosis drug use during the second and third months of gestation, i.e., in the critical period for most major congenital abnormalities, in case-control pairs did not indicate a teratogenic effect of these drugs in any group with congenital abnormality.

CONCLUSION: Maternal exposure to oral anti-tuberculosis drugs during pregnancy did not show a detectable teratogenic risk to the fetus; however, the number of pregnant women who were treated with these drugs during the critical period of most major congenital abnormalities was limited (six cases vs. 21 controls).