ABSTRACT
The following graphs relate crown rump length and developmental age to Carnegie stages 9 to 23 and will aid investigators in staging embryos. However, these correlations are affected by several variable factors and should not be regarded as being absolute. For example, there is a considerable spread of crown rump length within a given Carnegie stage (Figure 2), and, for the most part, the lengths given were made after fixation and are generally less than those of fresh specimens. The differing degree of curvature of embryos from about Carnegie stage 12 onwards influences the crown rump length. As shown by Juurlink and Fedoroff, 5 there may be considerable variation in the stage of development reached by embryos at any particular day of gestation (Figure 3) or incubation.
