Survey of neural tube defects in spontaneously aborted embryos.

Although variations in the incidence and types of central nervous system abnormalities have been demonstrated between early and late pregnancy, the reason for this finding has not yet been determined. Among 569 spontaneously aborted embryos, we describe 38 central nervous system lesions, many of which are different from those observed at birth. The importance of correlating morphology and cytogenetic studies in the understanding of pathogenesis of embryonic neural tube defects is emphasized.