title: The assessment of prenatal age from the crown-rump length determined ultrasonically.
abstract: Crown-rump lengths determined ultrasonically in vivo and in utero in cases of known postovulatory age (33-86 days) agree well with those in length/age tables in current embryological usage. Within the embryonic period proper, however, for a given age, the ultrasonic lengths are usually 1 to 5 mm longer than those of fixed specimens. The probable reasons for this are discussed.
mesh_terms: D001827:Body Height; D004622:Embryo, Mammalian; D005260:Female; D005865:Gestational Age; D006801:Humans; D008722:Methods; D011247:Pregnancy; D011296:Prenatal Diagnosis; D014465:Ultrasonics