Radiographic diagnosis of canine pregnancy: onset of fetal skeletal radiopacity in relation to times of breeding, preovulatory luteinizing hormone release, and parturition.

The onset and progression of canine fetal skeletal radiopacity were studied in relation to the times of mating, the preovulatory peak in serum luteinizing hormone (LH) levels, and parturition for each of 6 pregnancies. Lateral radiographs were obtained at 2- to 3-day intervals 30 days after mating and at 1- to 2-day intervals during the period fetal skeletons became radiopaque. Radiographs were assessed as to whether fetal elements were absent, barely discernible, distinct, or obvious. Fetal skeletal elements were 1st detected 20 to 21 days before parturition (42 to 52 days after mating and 44 to 47 days after the LH peak). Radiographs of fetal skeletons, sufficiently distinct for an unequivocal diagnosis of pregnancy, were obtained 17 to 20 days before parturition (43 to 54 days after mating and 46 to 49 days after the LH peak).