Problem:  Progesterone plays a central role during the maintenance of pregnancy. Our study aims to develop two hypoprogesteronic animal models using the 3beta-HSD inhibitor trilostane during early pregnancy.

Material and Methods:  Trilostane or vehicle was injected s.c. in DBA/2J-CBA/J female mice (4.5-8.5 dpc) or in ewes (5-16 day of pregnancy). Progesterone serum levels were assayed (mouse: 13.5 dpc; ewe: day 16). The resorption rate (RR), number of implantation sites (IS, mouse) or development of the conceptus (sheep) were analyzed.

Results:  Between trilostane-treated or control females progesterone levels did not differ in the mouse but, as expected, progesterone did not rise in the sheep model. Nevertheless, ovine conceptus development was not morphologically affected nor IS or RR in the mouse model.

Conclusions:  our data suggest that trilostane dose was insufficient to affect the reproductive success in our animal models. A more thorough analysis is currently undertaken in order to better characterize the phenotypes.