Two weeks later, at St Mary's Hospital in London, Jack was discovered to have a genetically inherited blood disorder called Christmas Disease, a form of haemophilia. Women carry the condition, and their sons - about one man in every 5,000 - have a 50 per cent chance of inheriting it.
Fran had been brought up with three sisters in the country in Norfolk. 'I thought of myself as a healthy, outdoor person who could do anything. Suddenly I was a haemophilia carrier, responsible for the pain my son was suffering. All my sympathy was with Jack, but even in those early days I felt uncomfortable about how little attention anyone was paying to women carrying haemophilia. No one saw being a carrier as traumatic in itself - because it is invisible, it is ignored. But from the moment they told me, I changed. I saw myself differently, as if I was contaminated.'
For the first year after Jack's diagnosis, Fran and Paul had little idea of what they were dealing with. The hospital had explained the condition, but how they managed living with a haemophiliac child was left largely up to them. The emphasis was on a bright and cheerful approach, with 'bleeds' portrayed as irregular events which could easily be put right. 'In that first year we were terribly isolated, and we craved the sight of a three-year-old boy with haemophilia running round perfectly fit, to show us it could be Jack's future. When we finally did make contact with other families there was enormous reassurance: it was clear that this generation of haemophiliacs have a much greater chance of fit and active lives.' In the concern with the medical implications of the disease, no one tried to untangle the guilt and unhappiness of the young mother.
'Being a carrier is completely disregarded. No one knows what to say to you,' says Fran. 'I even didn't want to tell my mother and sisters, because I felt they might hate me for putting them in the position where they might have to cope with discovering the same thing about themselves,' she says. (Her sisters have since tested negative; her mother has not been examined.) 'It's like haemophilia itself, once you start to talk about how terrible it makes you feel, it's like a bleed that won't stop. It's even too painful for Paul and me to talk about. It's like having a bomb inside you.'
Although Fran never spoke as frankly as this to her friends, those close to her knew she was suffering great strain. It was not surprising, then, that when she told them she and Paul wanted a second child, some said she must be mad.
'Most people thought we didn't know what we were doing. But although at first I was convinced that we should never have another baby, I came round to believing it was wrong for Jack to be an only child. He was already living in a world too dominated by haemophilia. I wanted him to have a sibling. If the child did not have Christmas Disease it would give us a more ordinary family life and take the spotlight off Jack. If the child also had haemophilia I felt that it would make Jack feel less isolated.'
Having decided to go ahead with a pregnancy, Fran and Paul also agreed not to have a test called chorionic villous sampling, which reveals a male foetus with haemophilia at nine weeks (after which a termination is available). Fran felt she could not undergo a termination, even though she supports the right of other women to do so. She saw her choice as being to have no more children or face the genetic lottery: a son would have a 50 per cent chance of having haemophilia, a daughter a 50 per cent chance of being a carrier.
Within a few days of the birth of George, her second son, Fran knew the worst: he too was haemophiliac. She admits now that there were times when she wondered if she had really prepared herself for such a blow. 'I sometimes imagine a day when he asks me why I had him, knowing he could suffer this disease. I can only tell him that we knew we would love him, and that I believed he could have a good life.'
If the opportunity for sex selection before conception had been available, ensuring that Fran could have had a girl, would she have taken it? She says that even with the benefit of hindsight her answer would be no.
'I feel angry when people say it would be all right if we had a girl. I know what it's like to be the carrier: it would put a sword of Damocles over her head. Sex selection on genetic grounds in haemophilia simply leaves all the anguish to the mother. It downgrades the impact of hereditary disease on women and shifts all the anxiety on to the next generation.
'I am very lucky in having a partner who has never once suggested I am to blame for our children's disease. But I would not want to put a girl into my situation in 20 years time, forced to make the same painful choices I have made.'
Fran now channels her grief and anger into supporting the fight to find a cure for the disease. 'Talking to other mothers, we all found that being responsible for the pain your child suffers is a great, unspoken burden. But in the midst of all the sorrow I am now even glad that I have had a second son with haemophilia: at least he and Jack can help each other. A daughter would be condemned to the guilt and loneliness which I live with every day.'