The assessment of gestational age and litter size in the guinea pig using a radiographic method

The gestational age and litter size in the guinea pig can be accurately assessed by taking an x-ray of the animal. From a measurement of the fetal head length on the x-ray plate a fetal weight can be calculated using previously accumulated data, included here. The gestational age can be assessed from this weight to within +/- two days, using the fetal growth data of Draper (1920), Eckstein, McKeown and Record (1955) and Ibsen (1928). The litter size can be readily ascertained from the x-ray plate.