Use of fetal biometry to determine fetal age in late pregnancy in llamas

Sixty-three pregnant llamas of known breeding date were used in this study. Forty-six of them were submitted to surgery between 186 and 320 days of gestation (52–91% of average gestation period, respectively). Under general anesthesia their fetuses were exteriorized and fetal weight (W), biparietal diameter (BPD) and femoral (F), tarsus-hoof (T-H), tibial (T)) and fronto-occipital (F-O) length were determined. Additionally, the same variables were determined on 16 newborn llamas. The weight was measured in kg and the length in cm. All the collected data was entered into a spreadsheet and different regression analyses as a function of gestational age (GA) were assessed. The best fit equations and their correlation for linear regression were the following: GA=169.448+16.66∗W, r=0.99; GA=−51.713+44.77∗BPD, r=0.88; GA=−72.139+39.48∗F-O, r=0.71; GA=39.304+8.35∗T-H, r=0.97; GA=91.276+8.23∗T, r=0.86; GA=102.029+9.94∗F, r=0.91. For multiple regression, the dependent variable GA can be predicted by the following equation: GA=67.462+11.163∗W+20.297∗BPD. Results of the present study indicated measured variables to be highly correlated with GA. This could be useful on daily basis in clinical examination of the neonates, in assessment of fetal growth and well being with cesarean sections, in the determination of GA in late gestation abortions, and in perinatal and reproductive research in the llama.