Prediction of parturition date through the evaluation of ultrasonographic fetal parameters in the bitch : dottorato di ricerca in scienze cliniche veterinarie : tesi di dottorato di ricerca

The aims of this thesis were the determination of the gestational age through ultrasonographic measurement of fetal parameters and the evaluation of their accuracy for the prediction of parturition date in different size dogs. The effects of litter size and fetal sex ratio on the accuracy were also investigated. Encephalic fetal brain structures were identified during pregnancy by ultrasonography and among these, the deep portion of telencephalic vesicle (DPTV) resulted easily measurable, because of its defined margins. Specific growth curves of DPTV were derived in small (≤10 kg), medium (11-25 kg) and large size dogs (26-40 kg). In bitches with unknown breeding dates, the accuracy of the prediction, obtained by the application of the formulae derived from the growth curves, resulted similar in different size categories. Moreover, no differences were observed in the accuracy obtained by the measurement of parameters that are usually adopted for predicting the parturition date during the first or the second half of pregnancy, respectively (inner chorionic cavity diameters, ICC; biparietal diameter, BP). These findings suggest that both parameters are equally reliable for prediction, regardless at what stage of pregnancy the bitch is examined. Although DPTV did not result as accurate as ICC and BP, it was easily detectable in the same ultrasonographic scan used for BP measurement. Thus, BP and DPTV can be measured at the same moment, without a further extension of the time of examination and DPTV may contribute to the improvement of the prediction of parturition day in those bitches that are examined during the second half of pregnancy. Concerning the effect of the litter size, the present thesis demonstrated that, using DPTV measurement, a higher accuracy was obtained in normal and large litter size compared to small litters. Moreover, although ICC accuracy was not affected by litter size, BP was significantly more accurate in normal litter size than in small and large litters. Fetal sex ratio did not affect the accuracy of the three parameters. In conclusion, this thesis demonstrated that prediction of parturition day obtained by ultrasonographic measurement of ICC, BP and DPTV is reliable when specific formulae for different size dogs are applied.