The Stages of Human Embryonic Development

Stage 20 scaled logo  

Stage 20 embryos have a greatest length of 18 to 22 mm and an estimated post-fertilization age of approximately 49 days. At this stage the upper limb is slightly bent at the elbow. The hands are still far apart and the fingers are short, stubby and slightly curved over the cardiac prominence. The interorbital groove is conspicuous.

Stage 20 - lateral view of Carnegie specimen #8157