Accuracy of abdominal radiography to determine fetus numbers in bitches at two gestational ages

Abstract

Abdominal radiography is considered the most accurate technique for determining fetal numbers. Nevertheless, there is a disagreement in the literature concerning the optimal time to perform the examination to obtain the most accurate fetal count. The objective of this study was to compare the accuracy of fetal counting in bitches at two gestational stages, using digital radiographs, and to analyze the possible complicating factors. Fifty-eight abdominal radiographs of 38 bitches at two gestational stages were analyzed by two observers. The first stage (Group I) included bitches between 45 and 48 days of gestation, and the second (Group II) bitches between 54 and 57 days of gestation. The Kappa index of agreement for categorical data indicated agreement between observers. Agreement was lower for Group I than for Group II. The estimated value of Pearson's coefficient for Group I was positive but weak for correlation between observers 1 and 2 and the number of puppies born. There was significant correlation between counts and the number of puppies born in Group II. We conclude that radiographic examination is not an accurate method of determining fetal number between 45 and 48 days of gestation and that the optimal time to perform this examination is between 54 and 57 days of gestation, at which time the fetal skull is fully visible on radiographs.