[Effects of methotrexate on early pregnancy in mice]

Single s.c. injection of MTX at dosages of 8, 24 and 72 mg.kg-1 on day 7 of gestation was found to have a feticide effect in mice. The mortality of fetuses on day 13 of pregnancy was 18.0%, 55.5% and 60.3%, respectively. Treatment with MTX caused a decrease of serum progesterone level on day 13 of pregnancy. Treatment with MTX at a dosage of 24 mg.kg-1 on day 7-9 of gestation terminated total early pregnancy. MTX combined with hCG 10 U/mouse or progesterone 0.2 mg/mouse was shown to have antagonistic effect to terminate early pregnancy. Synergism of RU486 combined with MTX on termination of early pregnancy in mice was observed.