Analysis of biochemical parameters in canine fetal fluids during the second half of pregnancy.

Although fetal fluids, amnion (AM) and allantois (AL), have been studied at the end of pregnancy in the bitch, little is known about their composition during gestation. The aim of this study was to characterize and compare the biochemical parameters of fetal fluids collected from healthy pregnant bitches in mid pregnancy. Fetal fluids were collected from 26 pregnant bitches between 35 and 62 days from ovulation based on ultrasonography. A total of 149 samples were analyzed; 94 samples of known origin (61 a.m. and 33 AL) from 17 dams, which included 17 paired samples (AM and AL from the same fetus; 34 samples), and 55 of unknown origin from nine dams. Reference ranges were formulated for 22 biochemical parameters in AM and AL based on the samples of known origin (n = 94). All parameters (creatinine, albumin, GGT and urea) significantly different between AM and AL were included (by mixed model ANOVA) in the analysis and an algorithm to predict the origin of the fluid was developed (by logistic regression). Overall, of the 94 samples, 79 samples (84%) were correctly identified by the algorithm. For the 33 allantois samples, and for the 61 amnion samples, 23 (69.7%) and 56 (91.8%) were correctly identified by the algorithm, respectively. Based on the algorithm, 31 of the unknown samples (58%) were classified as amnion and 22 samples (42%), as allantois fluid. For all the unknown samples, the average certainty was 86% (compared to 81% for the samples whose fluid type was known), showing the degree of precision of the classification.