Assessment of effects of mifepristone administration to lactating mice on the development and fertility of their progeny

Aim Mifepristone, a synthetic steroid compound that induces abortion, was recently found to potentially pass into human milk. This study aimed to determine the effects of mifepristone administration to lactating mice on the development and reproduction of their progeny. Methods Lactating mice were gavage fed with mifepristone (8 mg/kg) daily for 4 days either from days 1–4 or from days 7–10 of lactation; controls received only peanut oil. Growth, mortality rate, organ weight to bodyweight ratio, sex hormone at 20, 40 and 60 days, fertility of these F1 progeny and litter size, sex ratio and mortality rate of the second generation were recorded. Results No significant differences were observed in the average bodyweight, mortality rate of the female or male pups, and organ coefficient of uterus and ovaries of females in adulthood in comparison with the controls. However, the organ coefficient of testis at day 20 and 40 and testosterone concentration at day 60 were increased in male pups. Moreover, the reproductive capacity of the F1 pups was unaffected by 4 days exposure to mifepristone via their mother's milk: time to birth of F2 pups, litter size, sex ratio and mortality rate were similar to control F1 pups. Conclusion The study showed that treating lactating mice with 8 mg/kg mifepristone influenced only the organ coefficient of testis at day 40 and the testosterone concentration in male pups at day 60, however, it did not affect the development and fertility of female and male pups.