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A review of the mechanisms and evidence for typical and atypical twinning

journal contribution
posted on 2016-02-01, 00:00 authored by Helen C McNamara, Stefan C Kane, Jeffrey CraigJeffrey Craig, Roger V Short, Mark P Umstad
The mechanisms responsible for twinning and disorders of twin gestations have been the subject of considerable interest by physicians and scientists, and cases of atypical twinning have called for a reexamination of the fundamental theories invoked to explain twin gestations. This article presents a review of the literature focusing on twinning and atypical twinning with an emphasis on the phenomena of chimeric twins, phenotypically discordant monozygotic twins, mirror-image twins, polar body twins, complete hydatidiform mole with a coexistent twin, vanishing twins, fetus papyraceus, fetus in fetu, superfetation, and superfecundation. The traditional models attributing monozygotic twinning to a fission event, and more recent models describing monozygotic twinning as a fusion event, are critically reviewed. Ethical restrictions on scientific experimentation with human embryos and the rarity of cases of atypical twinning have limited opportunities to elucidate the exact mechanisms by which these phenomena occur. Refinements in the modeling of early embryonic development in twin pregnancies may have significant clinical implications. The article includes a series of figures to illustrate the phenomena described.

History

Journal

American journal of obstetrics and gynecology

Volume

214

Issue

2

Pagination

172 - 191

Publisher

Elsevier

Location

Amsterdam, The Netherlands

eISSN

1097-6868

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2016, Elsevier