Prediction of gestational age based on foetal ultrasonographic biometric measurements in light breed horses.

A table was generated, based on foetal ultrasonographic measurements in light breed mares, for each day of gestation beginning with day 100, to provide the predicted value of four biometric parameters: biparietal diameter (BPD), eye approximated volume (EyV), foetal aortic diameter (AortD) and femur length (FL). Using this table, day of gestation was successfully predicted in 23 Quarter Horses (QH) with known mating or ovulation dates. BPD, EyV and FL were the best foetal age predictors between 100- and 200-days gestation predicting within 2 weeks of the actual day of gestation, while BPD and EyV were best between 200 and 300 days (within 3 weeks), and EyV was best after 300 days (within 3 weeks).