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Twin sisters born with condition so rare they’ve won Guinness World Record
Twin sisters born with condition so rare they've won Guinness World Record,Sienna and Sierra Bernal, both 23, from Texas, US, shocked doctors when one of them was born with primordial dwarfism. Thanks to this diagnosis they've won a Guinness World Record

Twin sisters born with condition so rare they’ve won Guinness World Record

A woman born with a condition so rare won a Guinness World Record with her identical twin sister.

Twin sisters Sienna and Sierra Bernal, both 23, from Texas, US, shocked doctors when only Sienna was born with primordial dwarfism, which is practically unheard of.

Thanks to this diagnosis, the identical sisters hold the record title for the rarest form of discordant twinning.

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The phrase "twin growth discordance" refers to a large size or weight disparity between the two foetuses of a twin pregnancy.

The smaller twin's estimated foetal weight must be below the 10th percentile in order for it to be classified as a growth discordance.

Sierra weighs 7st and stands at 5ft 7in, while Sienna weighs 3.5st and measures 4ft 4in.

Sienna was born with primordial dwarfism
Sienna was born with primordial dwarfism (Image: Guinness World Records)