Eight pregnancies in five queens were followed with serial ultrasound examinations. Measurements of head and body diameter were made throughout pregnancy. These measurements were used to produce individual growth curves for each pregnancy and average curves for both head and body diameter. Formulas based on the slope of the growth curves were derived. These formulas were then used to predict parturition dates based on single measurements of fetal head and/or body diameter in eight additional queens. Predicted date of parturition was then compared to actual queening dates. Ultrasound prediction of parturition date was accurate to within two days in seven of eight queens.