Fetal demise and delayed parturition following post-mating administration of depot progesterone for contraception in three hunting dogs.

Depot medroxyprogesterone acetate (MPA) is used in dogs to suppress estrus or prevent pregnancy. This report describes three cases in which post-mating administration of MPA resulted in failure of parturition and fetal death in hunting dogs. In all cases, MPA was administered within 1-7 days post-mating at a fixed dose of 150 mg. The dogs presented with signs of prolonged pregnancy and absence of labor. Ultrasonographic examinations confirmed the presence of non-viable fetuses, and ovariohysterectomy was performed in each case. In these dogs, serum progesterone concentrations ranged between 2.20 and 9.03 ng/mL at the time of parturition and remained within this range for up to two weeks postpartum. These hormonal alterations were likely due to exogenous MPA, which interfered with luteolysis, delaying the onset of labor. These findings underscore the importance of restricting depot progesterone use to appropriate reproductive stages to prevent iatrogenic reproductive failure and to ensure animal welfare.