Evaluation of serum C-reactive protein concentration as a marker of impending parturition and correlation with progesterone profile in peri-partum bitches.

C-reactive protein (CRP) is one of the major acute phase proteins in dogs. It is produced by the liver and rapidly increases in response to an inflammatory stimulus. The aim of this study was to measure CRP concentrations around parturition and to verify whether this protein could be useful, together with progesterone (P), to detect the onset of parturition in bitches. The CRP and P concentrations were measured in 66 serum samples from 28 healthy pregnant bitches, collected between -5 and +2 days from parturition (day of parturition = day 0). The effect of 'days from parturition', parity, and litter size on P and CRP concentration was analyzed and the correlation between CRP and P values was calculated. The P and CRP values were affected by 'days from parturition'. While P decreased during the last days of pregnancy, CRP concentration was greater than the normal range (0-1.07 mg/dl) starting the parturition day with the increase starting on day -1. The CRP concentration profiles during the days around parturition have not been previously reported in dogs. The increase in CRP very near the time of parturition and the low magnitude of the increase do not allow for it to be useful in clinical practice to assess the onset of parturition in the bitch.