A mother plans to freeze her eggs so that her infertile daughter may someday be able to use them to give birth to her own brother or sister.
Toddler Mackenzie Stephens was born with Turner Syndrome, a hereditary condition which means she is missing an X-chromosome.
The condition, which only affects girls, means two-year-old Mackenzie was born without ovaries, preventing her from ever having a child of her own naturally.
When Penny Jarvis, herself a mother of five, learnt that her daughter might never be able to have children of her own, she was devastated.
So Ms Jarvis, 25, has decided to freeze her own eggs so someday Mackenzie can use them for IVF and start a family.
However, technically, this means Mackenzie's future child would be both her offspring and her sibling.
Ms Jarvis described how she and partner Karl Stephens, 42, were distraught when the doctor broke the news about their daughter's condition.
The full-time mother from Sheffield, said: 'The doctor was talking about chromosomes and things and it was all a bit of a blur.
'The only word I heard at the time was 'infertility' and I just burst into tears. It's what most people want to be; a mum.
'She has three sisters and I couldn't imagine her growing up and watching them all have children while she couldn't have any of her own.
'Obviously, every mother wants to be a grandmother someday - that's what they dream of.
'As I was leaving the hospital, the consultant told me not to look up Turner Syndrome on the internet as it was full of worst-case scenarios.
'But, of course, I did it anyway. As soon as we were over the shock, Karl and I looked it up together as we had never even heard of it before and neither had any of our friends.
'While some of the stuff I was reading was scary - talk of congenital heart defects and diabetes - I discovered that egg donation was a possibility.'
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Mackenzie has Turner Syndrome, which means she doesn't have ovaries
Turner Syndrome affects one in every 2,500 girls. It causes a number of mental and physical health issues, but most can be corrected or treated with surgery, drugs and psychological therapy.
The most common symptoms are swelling of the limbs, small stature and infertility. Mackenzie, who requires a daily dose of growth hormone, is also partially deaf and uses Makaton sign language to communicate as she suffers from speech problems.
She also has severe mood swings and sees a behavioural psychologist. It is hoped these will improve as she gets older.
Her mother dreams that someday she will fall in love and start a family of her own. When the time comes, Penny said, the option will be there for her to use her mother's eggs to have a child.
Mothers only have a short period in which they can make the donation to their daughters because, by the time they reach the age of 40, their eggs are likely to be of too poor quality to store.
However, medical advances in recent years have made it possible to store the eggs for longer periods.
The practice has been criticised by some ethicists who fear that it could cause the daughters psychological problems, while the resulting children could be confused about their relationship to their mother and grandmother.
But Penny, who has four other children; Jaymie-Leigh, five months, Morgan, six, and twins William and Abigail, three, said that any mother would do the same for their child.
She said: 'You could look at it as Mackenzie giving birth to her own brother or sister, but I choose not to see it like that.
'You do the best for your children and Mackenzie's daughter or son would be her own.
'It's a comfort to know that if she did have a child they would still have part of her own genetic make-up as well, so it would still be a part of her.
'I'd like to think her sisters would offer their eggs too. But if they didn't, at least the option would be there for her.
'A few people have told me they think it's a bit sick, but on the whole people have been supportive.
However, while Penny is confident she is doing the right thing for her daughter, some medical experts are less sure.
Josephine Quintavalle of Comment on Reproductive Ethics (CORE) said: 'One can fully understand the sadness for a mother to discover that her little daughter suffers from Turner Syndrome, but I do not think putting her own eggs in the freezer is either a practical or an ethical solution.'
She said there was a possibility that Turner Syndrome could be passed on genetically and therefore most doctors would not want to use the grandmother's eggs.
Ms Quintavalle added: 'Social and ethical objections are equally compelling.
'A child born in this way would be a half-sibling of the birth mother, her husband having fertilised the eggs of his mother-in-law.
'Psychologists are already talking about the trauma of genealogical bewilderment, as egg and sperm donation and surrogacy create more and more artificial conceptions.'
A spokesman for the Human Fertilisation and Embryology Authority added: 'When providing treatment, it is important that account has been taken of the welfare of any child who may be born as a result of the treatment and of any other child who may be affected by the birth.'
