Effect of a steroid contraceptive, "Enidrel" on the pre- and postnatal development of rats

To determine the long-term effects of prolonged and intensive treatment with an anticonceptive steroid, 60 female Wistar rats were given 1 mg/kg/day Enidrel (norethynodrel plus ethinyl estradiol 3-methyl-ether) by gastric sound for 60 days. The animals were divided into 2 groups and were placed with males for 10 days. Group 1 continued to recieve Enidrel through mating to the 15th day of gestation; Group 2 received no further treatment. General behavior and weight of the animals was unchanged when compared with controls. There were profound disturbances in the estrous cycle, but couplings and number of impregnations were normal in both groups. Most of the females in Group 1 aborted normal fetuses between Gestation Days 8 and 15; those in Groups 2 continued to term. Group 1 animals were remated and siblings of the 1st generation were crossed. The animals were fertile and the ne onates developed normally. It is concluded that Enidrel had no effect on morphogenesis and no masculinization effect on the hypophyso-hypothalamic system, as evidenced by the normal sexual behavior and fertility of the females.