Correlation between fetal age and ultrasonographic measurements during the second half of pregnancy in domestic cats (Felis catus).

We ultrasonographically evaluated the prenatal development in cats, from Day 30 to the end of pregnancy, subjecting a group of pregnant cats (n = 8) to daily ultrasonographic examinations. The ultrasonographic images allowed us to measure the diameter of the fetal abdomen, the biparietal diameter of the fetal skull and the diameter of the fetal stomach. A correlation between these measurements and gestational age was found with a linear, parabolic and exponential regression analysis. From Days 38 to 43 after breeding we also performed fetal gender determination by evaluating the external genitalia. All queens successfully carried their pregnancies to term. This study compiled useful new data in order to clinically monitor the normal course of pregnancy in cats and to determine gestational age.