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Doctors have confirmed that two four-year-old children in Brisbane, Australia, are “semi-identical” twins, making them just the second case of this type of twin ever reported. The boy and girl, described today (February 28) in the New England Journal of Medicine, share identical DNA from their mother’s side, but only some DNA from their father’s side—a situation the authors suspect arose by two sperm cells fertilizing the same egg simultaneously.
“This is confirming there is this third type of twinning where it’s not fraternal and it’s not identical,” study coauthor Michael Terrence Gabbett of Queensland University of Technology in Brisbane tells Reuters Health. “It’s this strange place in between.”
The case was spotted after doctors took ultrasound scans of the mother’s womb. “The mother’s ultrasound at six weeks showed a single placenta and positioning of amniotic sacs that indicated she was expecting identical twins,” study coauthor ...
