Five-year-old Reuben Blake has already started school, but his 'twin' sister Floren, conceived during the same IVF treatment cycle, has only just been born.
Jody and Simon Blake sought fertility treatment from the Bristol Centre for Reproductive Medicine in September 2005, and the treatment led to the birth of their son Reuben in December 2006. Floren was one of three spare embryos which were kept frozen until the couple decided to try for a second baby five years later.
'I find it very difficult to resist the temptation to say, "Oh, and by the way they are twins"', said Simon Blake, Floren and Reuben's father. 'It's hard to comprehend that a life could come from material that's been frozen for that length of time'.
Floren is the product of the only one of the three frozen embryos which survived. The frozen storage of spare embryos for up to ten years is relatively common in the UK as it allows the embryos to be used in future IVF treatments, avoiding the risk or expense associated with fertility drugs or a further round of egg collection.
'We very often recommend storing surplus embryos so that they can be used at a later date', said Dr Valentine Akande, director of fertility services at the Bristol Centre. But, he added, 'not everybody is able to have those surplus embryos and, of course, not everybody meets with success when they are used'.
The Human Fertilisation and Embryology Authority, the UK regulator for fertility treatments, says that current evidence suggests that there are no long term health problems associated with children born from frozen embryos, regardless of how long they have been stored for.
Children conceived by IVF have a greater chance of being one of a pair of twins. Often two embryos are implanted at once to increase the chances of a successful pregnancy. Should both embryos reach full term non-identical twins will be born. There is also some evidence to suggest that IVF treatment increases the likelihood of having identical twins after one fertilised egg divides into two embryos. Neither of these scenarios apply to Reuben and Floren.