Chloroquine and premature evacuation of uterine conceptus in rats

Bilateral spaying on day 18 of pregnancy in rats made the refractory uteri highly reactive to a single injection of chloroquine (25 mg/kg). Complete evaluation of the uterine conceptus resulted by 24-48 hours following chloroquine administration. It was moreover observed that the amount of luteal progesterone which was found to be sufficient to maintain pregnancy until term, failed to reverse the abortifacient efficacy of chloroquine.