(WALSALL, England) -- Ryleigh Shepherd was conceived in 1998, the same year as her 11-year-old twin sisters, but she wasn't born until 2010.
The three girls from Walsall, in Great Britain, who were born more than a decade apart in two different centuries, are actually triplets. All were the product of in vitro fertilization (IVF) and came from the same batch of frozen embryos. Ryleigh came from the same group of embryos that had allowed her parents -- Lisa and Adrian Shepherd -- to give birth to twins Megan and Bethany.
British experts say they know of no other case in which three siblings from the same round of fertility treatment have been born with such an age gap.
How long embryos can be frozen and still viable is still not known, but American fertility experts say they have great confidence in the success of new reproductive techniques.
"It's incredibly common for people to go back a second and third time," said Barbara Collura, executive director of RESOLVE, the National Infertility Association. "There have been recorded cases of kids born far longer apart. This doesn't tip the scales."
Fertility experts estimate that about 400,000 embryos are currently in frozen storage in the U.S., and a more comprehensive survey will be underway in the spring.
Copyright 2010 ABC News Radio