Considerations of antibiotic therapy during pregnancy.

The use of antibiotics in pregnancy requires that the clinician consider both toxicity to and pharmacokinetics for mother and fetus. Although most adverse reactions to antibiotics in the adult are not modified by pregnancy, those to tetracycline and erythromycin estolate are the exceptions. Tetracycline is contraindicated throughout pregnancy because of fetal effects, whereas sulfa preparations, trimethoprim, and chloramphenicol are contraindicated only at specific times during gestation. The pharmacokinetics of antibiotics in the mother are such that lower serum concentrations are achieved for a given dose, which may be important in serious or resistant infections. Fetal kinetics are such that transfer to amniotic fluid and distribution within the fetus may not provide adequate protection for the fetus in cases of chorioamnionitis.