Table 2.

Summary of the historically most important methods used for the estimation of the post-fertilization age of human embryos and the resulting age proposals for CS-10 embryos.

Data/Methods Used for the Estimation of the Post-Fertil. Ages	Proposed Post-Fertil. Ages of CS-10 Embryos
Menstrual history/calculations according to the Reichert-His convention (~1880–1910)	13–14 days [48,52,53]
Menstrual history/calculations according to concepts of intermenstrual ovulation (~1900–1940)	21–24 days [67] 20–22 days [68]
Morphology-based staging/comparison with macaque embryos of known ovulation age (since~1940)	21–23 days [9,14]
Menstrual history/calculations according to the concept of mid-cycle ovulation (since~1940)	20–23 days [63] 26–28 days [64]
Greatest length of human embryos from the Carnegie Collection/ comparison with the embryonic growth curves obtained from first trimester sonographic examinations (since 2010)	28–30 days [47]