Postimplantation increase in plasma fibrinogen concentration with increase in relaxin concentration in pregnant dogs

To determine time courses of pregnancy-related changes in plasma fibrinogen, serum relaxin, and serum C-reactive protein-like immunoreactivity (CRP-LI) concentrations in pregnant and nonpregnant dogs.

16 pregnant and 13 nonpregnant Beagles, 6 pregnant Beagles, and 3 pregnant and 3 nonpregnant dogs of other breeds.

Fibrinogen was measured by nephelometric centrifugal analysis of light scatter in plasma samples of all dogs, and CRP-LI was measured by fluorescence immunoassay in selected sera from 10 pregnant and 10 nonpregnant dogs. Relaxin was measured in selected sera from 7 pregnant and 7 nonpregnant dogs.

During pregnancy, fibrinogen concentration increased between days 21 and 30 after the luteinizing hormone surge, and was > 280 mg/dl between days 29 and 50 in 84 of 86 samples, with peak values 539 +/- 29 mg/ dl higher (P < 0.01) than those in nonpregnant dogs (188 +/- 8 mg/dl), higher values from days 21 to 50 (P < 0.01) than those in nonpregnant dogs, and values similar to those in nonpregnant dogs after day 50. Relaxin concentration was increased from days 26 to 30 and 0 to 4 days after fibrinogen concentration increased in pregnant dogs, and was not detectable in nonpregnant dogs. The CRP-LI concentration was higher in pregnant dogs at days 26 to 50, but values were inconsistent within and among dogs, and near the limit of sensitivity of the assay.

Concentration of the acute-phase reactant protein fibrinogen increases after day 20 following implantation in dogs, at or just before the pregnancy-specific increase in relaxin concentration from days 26 to 30, and persists until day 50.

Fibrinogen assay may be useful for pregnancy diagnosis in dogs.