title: Variability in human embryonic development and its implications for the susceptibility to environmental teratogenesis.
abstract: Considerable variability is observed in the size and developmental stage among human embryos at a given gestational age, suggesting that prenatal development does not proceed at the same speed in every embryo. Such variability in embryonic development seems to occur in many (probably all) animal species, and is probably a normal "biologic" phenomenon to some extent. In the case of humans, some other factors (e.g., maternal memory bias, difficulty in assessing the timing of ovulation and fertilization) make it more difficult to assess the developmental stage of embryos in utero. Such facts related to human embryonic development should be taken into account when the teratogenic risk of a human embryo is considered.
authors.affiliation: Department of Anatomy and Developmental Biology and Congenital Anomaly Research Center, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan. shiota@hq.kyoto-u.ac.jp
authors.forename: Kohei
authors.initials: K
authors.lastname: Shiota
mesh_terms: D004622:Embryo, Mammalian / Q000187:drug effects / Q000196:embryology; D047108:Embryonic Development / Q000187:drug effects* / Q000502:physiology*; D004781:Environmental Exposure; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D013723:Teratogens / Q000633:toxicity; D013792:Thalidomide / Q000633:toxicity
chemical_list: D013723:Teratogens; D013792:Thalidomide