title: Indirect estimation of crown-rump lengths of incomplete conceptuses from analysis of spinal-cord dimensions.
abstract: The spinal cords of serially sectioned human embryos and early fetuses, ranging from 4mm to 112mm in crown-rump length, were examined in order to determine whether a mathematical relationship exists between certain spinal-cord dimensions and the crown-rump length of the conceptus. This information may be useful in estimating the crown-rump length, and hence the gestational age, of advanced human embryos and early fetuses when direct measurement is impossible. Five widely-spaced levels along the spinal cord were studied, but only those data relevant to the levels of the first thoracic (T1) and twelfth thoracic (T12) vertebral bodies are described in detail. Similarly, although eight distinct spinal-cord dimensions were measured at each level, only those measurements that bore a high enough correlation with crown-rump length to be of any predictive value are presented here, the most useful being the maximum spinal-cord width and the maximum grey-matter width, both of which increased with gestational age in a highly predictable way. The descriptive account of the morphological appearance of the cord at these levels also enables, though less accurately, an estimate of the crown-rump length of a conceptus to be made by direct inspection of a single transverse section through the thoracic region of the cord. The predictive value of these observations is discussed.
mesh_terms: D000886:Anthropometry; D004622:Embryo, Mammalian / Q000033:anatomy & histology; D005333:Fetus / Q000033:anatomy & histology*; D005865:Gestational Age; D006801:Humans; D013116:Spinal Cord / Q000196:embryology*