Applicability of fetal heart rate variation, umbilical artery resistivity index and maternal body temperature for predicting imminent parturition in bitches.

This study aimed to evaluate the applicability of fetal heart rate variability (FHRvar%), umbilical artery resistivity index (RI-UmbArt), and maternal body temperature (Temp, °C) for predicting parturition in bitches. Fifteen bitches (1-6 years old) were included. Gestational age was estimated using fetal biometry (inner chorionic cavity or biparietal diameter), and during the last week of pregnancy the animals were evaluated twice daily until parturition. Data were retrospectively grouped according to the hours before parturition (HBP). The evaluated parameters were FHRvar% (measured over 5-10 minutes using pulsed Doppler abdominal ultrasonography), RI-UmbArt (assessed by triplex Doppler in three fetuses per session), and Temp (rectal thermometry). Data were statistically compared and correlated with HBP. FHRvar% showed a gradual increase (P = 0.010) beginning at 84 HBP, reaching a peak between 24 and 12 HBP, whereas Temp significantly decreased during the last 24 HBP (P < 0.001). Both FHRvar% and Temp were significantly correlated with HBP (P < 0.001); however, these correlations were weak (Pearson's r = -0.338 and -0.491, respectively). RI-UmbArt showed no significant variation across HBP (P = 0.711). An FHRvar% > 31.5% predicted parturition within 24 hours with a sensitivity of 65% and a specificity of 67%, whereas a Temp < 37.5°C predicted parturition with 69.6% sensitivity and 77.8% specificity. In conclusion, although FHRvar% and maternal body temperature are influenced by the proximity of parturition, they may not be reliable predictors of parturition timing, while RI-UmbArt appears to remain unchanged close to delivery.