Clinical use of fetal measurements to determine the whelping day in German shepherd breed bitches

The aim of this work was to use a linear regression model previously developed in a pilot study to calculate days before parturition (DbP) using inner chorionic cavity (ICC), biparietal diameter (BPD), crown-rump length (CRL), body diameter (BD) and deep portion of telencephalic vesicle (DPTV) in German shepherd dogs (GSD) with known ovulation day and then to test that model in bitches with unknown ovulation day. In our current study, a model for GSD bitches published in a previous report, proved satisfactory for ICC [DbP=44.76-(4.34×ICC)] and BPD [DbP=38.65-(12.86×BPD)]. We therefore used their model, but developed a new one for CRL, BD and DPTV. For ICC and BPD, we tested accuracy for more than 35days before parturition (ICC) and more than 15days before parturition (BPD). Measurements were taken on at least two fetuses during each ultrasound recording (US) of 22 GSD bitches with known (n=16) and unknown (n=6) ovulation days. The accuracy of the above model was 77-100% for ICC and 83-96% for BPD with a precision of ±1 and ±2days, respectively. Accuracy increased significantly when US was performed more than 35days before parturition for ICC and more than 15days before parturition for BPD. BD and CRL were the most accurate parameters (R(2)=0.95 and 0.85). In bitches with unknown ovulation day, BD accuracy was 71.4-100% with a precision of ±1day and ±2days, respectively. CRL and DPTV were less accurate (±1day, 60%; ±2days, 80% accuracy).