Age determination of the fetal and neonatal pigtailed macaque (Macaca nemestrina) from somatometric measurements.

Crown-rump length, foot length and body weight were measured on 134 pigtailed macaque (Macaca nemestrina) fetuses and neonates between 50 and 176 days of gestation. Regression analysis was performed and linear equations generated that described the relation of age to each linear measurement. From the equations, best fit curves (sex-combined for the linear dimensions and sex-specific for weight) were drawn. The three variables were all highly correlated with gestational age, with the standard error of the estimate 1 week or less in each case. On the basis of accuracy of age prediction, reliability and simplicity of measurement, foot length was the best linear measurement for determining age, particularly after 100 gestational days.