In 1994, Susie Duce gave birth to her second child, a little girl called Melissa. But almost as soon as she held her baby, Susie knew something was wrong. Melissa was, says Susie, floppy. "She hardly moved. The doctors insisted she was fine, but I knew she wasn't. She couldn't even hold her head up at six weeks."
Eventually, aged four months, the diagnosis came: Melissa had spinal muscular atrophy (SMA), a rare genetic disorder that neither Susie, her husband Kevin, nor any family member had ever heard of. To their horror, Susie and Kevin discovered that they both happened to carry a recessive gene which means that any child they have together has a one-in-four chance of being affected by SMA. Many such babies die when they are only days old. Few live beyond a year.
Melissa was nursed at home, 24 hours a day, by her parents. She died aged nine months.
Last month, though, at St Thomas's hospital in London, Susie gave birth to Isobel, James and Kieran, all free of the SMA gene. The triplets were born thanks to a relatively new technique called preimplantation genetic diagnosis (PGD). You've probably heard of PGD from headlines decrying "designer babies" or "eugenics". It's controversial because it involves the genetic testing of embryos before they are implanted in a woman's body, so as to screen out certain hereditary diseases. This may sound threatening, but as Susie puts it: "PGD is only about having a 'designer baby' if 'designer' means one that lives."
Concern about genetic manipulation is understandable. A couple of years ago we were panicking about cloned sheep and posthumous fathering. Last week, there was the furore over the news that women's eggs can now legally be frozen then defrosted for use years later. But PGD isn't about creating a blue-eyed super race. It is currently only used - in Britain, at least - to screen out specific, highly disabling (and usually lethal) disorders like SMA, cystic fibrosis and haemophilia. It can also help women like Tracy. Tracy has been trying for 10 years to have a baby. She had four miscarriages before doctors discovered that an abnormality in her chromosomes (a genetic condition called "translocation") means she'll either keep miscarrying, or have a severely disabled baby who will then die. Thanks to the centre for preimplantation genetic diagnosis at Guy's and St Thomas' hospital, Tracy is now 22 weeks pregnant - also, amazingly, with triplets.
PGD does not involve any genetic alteration of embryos and is strictly regulated in Britain by the human fertilisation and embryology act. A treatment begins with IVF to generate and fertilise several eggs. One cell is then taken from each embryo a few days after fertilisation and tested to see whether it - and by extension the embryo itself - is free from the disorder. Three healthy embryos are then implanted in the woman's uterus (one or two usually won't take hold, so triplets aren't the norm). If all goes well, the result is a healthy child.
The concept of testing a foetus for genetic disease, though controversial, is not new. Tests during a pregnancy - either amniocentesis, performed at 18 weeks or chorionic villus sampling, done at 12 weeks - have long been able to detect genetic disorders. So, both Susie and Tracy could have become pregnant naturally and chanced the outcome. Tracy would undoubtedly have miscarried before 12 weeks. Susie, though, could have undergone the tests (which themselves can cause miscarriage). If SMA had been found, she would have been offered a late abortion. Or she could have given birth and then watched her child die, as she did Melissa. Susie's response is understandable: "Pregnancy was out of the question. We couldn't handle losing another child." She could have tried sperm or egg donation. Or adoption. Or she could have resigned herself to having no more children. Or there was PGD, available in only four clinics in Britain.
Yvette and her husband Alfie face the same choice. In 1997, their son Callum died of SMA at 11 weeks. With eight healthy nephews and nieces, it didn't occur to Yvette that her baby would have anything wrong with it. "When you hear you're having a baby, the last thing you expect is that it'll die," she says. In 1998 their daughter Georgia was stillborn, also with SMA. Yvette "can't face losing another child". So, she applied for funding from her health authority to try PGD.
One cycle of the treatment at St Thomas's (which is not profit-making) costs £2,500. But Yvette, like Susie before her, was told by her health authority that funding wasn't available. Susie had battled for two years for funding believing that "if I didn't get it, no one else was going to". Both health authorities mistakenly maintained that PGD was "fertility treatment". Both offered to pay for as many abortions as the women "needed". Both - eventually - paid up. Yvette and Susie hope that other health authorities will be less reluctant to fund PGD in future.
More than 300 children have been born this way in 30 clinics world-wide since the technique was developed in the late 80s. And last week the team at St Thomas's were celebrating the birth of their eighth PGD baby since the programme began in 1997. "Our high success rate," says Professor Peter Braude, director of the PGD programme, "is down to close collaboration with geneticists at Guy's hospital, one of the largest departments in the country devoted to human genetics." Currently, 33% of women having one PGD treatment there become - and stay - pregnant.
People who believe that life begins at conception will, of course, consider it unacceptable to screen embryos, whatever the reason. Many people living with hereditary diseases, or relatives who have them, also object to PGD on ethical grounds. But those who fear future abuse of these advances probably needn't worry. The human fertilisation and embryology authority (HFEA), the body that regulates PGD, has banned any non-medical uses. "[We] do not think it would be acceptable to test for any social or psychological characteristics, normal physical variations or any other conditions which are not associated with disability or a serious medical condition," says Ruth Deech, who chairs HFEA. Furthermore, HFEA is currently circulating a document to ask us - the public - what we think of PGD.
And, according to the experts, the notion of screening for intelligence is (and will be for the foreseeable future) a genetic impossibility. "We have not even identified any of the principle genes responsible for intelligence," says Christine Gosden, professor of medical genetics at Liverpool university "let alone been able to understand how they interact and then manipulate them." (Intelligence, apparently, results from the subtle interaction of more than 1,000 unknown genes). What's more, as prof Braude points out: "If you were going to design babies, PGD would be an extremely inefficient way to do it." It would be pretty impossible to isolate specific, "desirable" characteristics from the few embryos that one person could produce.
What PGD does offer, though, is the chance for women like Yvette, Susie and Tracy to have a baby who won't suffer from a fatal hereditary disease. Yvette's first cycle of treatment hasn't made her pregnant, but the medical team are optimistic about the next one. Yvette and Alfie, meanwhile, hope "that it will be the answer to our prayers".
• For more information on PGD at St Thomas's, call Dr Helen Bickerstaff on 0171 960 5878. The HFEA consultation document is posted on the HFEA's internet site: www.hfea.gov.uk
