Fertility, reproduction and postnatal survival in mice chronically exposed to halothane

Reproductive studies were performed in Swiss/ICR mice chronically exposed to subanesthetic and anesthetic concentrations of halothane. Male and female mice were treated five or seven days a week for nine weeks prior to mating; exposure of females was continued daily throughout pregnancy. Halothane exposures were 0.025, 0.1, 0.4, 1.2, and 4.0 MAC hours per day. No adverse effect on reproduction was observed at the lowest two exposure levels studied. Exposures to 0.4 MAC hour per day or more were associated with decreased maternal weight gain, fetal fetal length and weight, and early postnatal weight gain. Pregnancy rate, implantation rate, and number of live fetuses per litter were significantly decreased at 1.2 MAC hours per day. The percentage of resorption or fetuses dead in utero was not increased, and postnatal survival of offspring was unaltered. Subsequent matings between untreated females and males exposed to halothane, 1.2 MAC hours per day for 17 weeks, resulted in normal reproductive performance; this suggests that the adverse reproductive changes observed when both males and females were exposed represented a primary effect on females. The least exposure at which effects were seen is approximately 40 times greater than the level of human occupational exposure is unscavenged operating rooms.