Twinning handedness and embryology.
It is hypothesized that in some pairs of monozygotic twins, the biological insult occasioning the split may also cause a reversal of predetermined handedness and that this cannot happen if the split occurs before the ovum itself has acquired laterality. The use of the word 'split' here is not meant to give support to the concept of mirror-imaging.
D004622:Embryo, Mammalian / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D011247:Pregnancy; D014430:Twins, Monozygotic