Four (100, 200 mg/kg) or 3 (1000 mg/kg, two with implantation sites) inseminated Wistar rats were treated daily by gavage with 100, 300 or 1000 mg of LKA 3957/kg body weight/day in 0.5% carboxymethylcellulose in demineralized water from day 6 to day 19 p.c. The fetuses were delivered by cesarean section on day 20 p.c. Investigations were performed on the general tolerance of the test compound by the females as well as on its effects on intrauterine development (pregnancy rate, number of fetuses and resorptions, external findings in the fetuses, fetal weight, and fetal skeletal malformations and variations (wavy ribs only)). Appearance, behavior, mortality and feed consumption for the females in the 100 mg/kg dose group were unaffected. Furthermore, there was no clear effect on body weight development in this dose group.