writing in Europe's leading reproductive medicine journal Human Reproduction, report (Tuesday 25 May)
[PDF] what they believe to be a world record – a baby born using sperm that had been frozen for 21 years.
"We believe this is the longest period of sperm cryopreservation resulting in a live birth so far reported in the scientific literature," according to one of the authors, Dr Elizabeth Pease, Consultant in Reproductive Medicine at the Department of Reproductive Medicine at St Mary's Hospital, Manchester.
A healthy baby boy was born two years ago to a couple after the father had been successfully treated for testicular cancer with surgery, radiotherapy and chemotherapy between 1979 and 1981.
Following diagnosis at the age of 17 but before treatment, which was to leave him sterile, five ampoules of sperm were frozen. Long term storage continued until he married and wished to have a family. ICSI – the technique that involves a single sperm being injected into an egg – was used to fertilise his partner's eggs. The baby was born after the fourth IVF cycle, when two of the embryos that had been frozen at the start of IVF treatment were transferred to his partner's uterus.
"Even after 21 years of storage, the percentage of motile sperm after thawing was high," said Greg Horne, Senior Embryologist. "This case report provides evidence that long-term freezing can successfully preserve sperm quality and fertility. This is important to know because semen stored by young cancer patients is undertaken at a time of great emotional stress when future fertility is unlikely to be an immediate priority.
"It also suggests that we need to extend follow-up studies of cryobanked sperm up to 25 years at least. A recent study showed that only 27% of men who stored semen at our centre prior to cancer treatment used their samples within 10 years, and in the UK regulations allow sperm to be stored until a man is 55."
The couple, speaking anonymously, were keen that their case be reported as an example of the safety and success of long-term sperm freezing and to help encourage young cancer patients to think positively about the future at a time when they are under considerable emotional stress because of their diagnosis and impending treatment. They were also anxious to point out that had it not been for sperm banking and IVF treatment being available on the NHS they would not have had the opportunity to become parents.
Cryopreservation is the storage of biological materials in a constant steady state at extremely cold temperatures. The biological material is combined with a cryoprotectant substance formulated to protect the cells from damage during the freezing and subsequent thawing cycles. The cells remain frozen at -196°C (-321°F) until needed.