The operation was carried out by Kypros Nicolaides, professor of foetal medicine at King's College hospital in south London. He performs more embryo reductions than any other doctor in Britain - more than 140 in the past eight years - cases that are referred from all over the country. The procedure, carried out under local anaesthetic and using an ultrasound scan, involves inserting a needle through the stomach into the uterus and injecting potassium chloride into the embryo's chest until its heart stops beating. At King's, the operation is performed eight weeks into the pregnancy when the embryos are little more than a centimetre in length.
Professor Nicolaides says the operation has unarguable medical benefits. "With multiple pregnancies, there is a great risk of miscarriage and of severe prematurity. Embryo reduction halves the risks of both." But he admits it is a terrible decision for parents to have to make. "When couples come to me with multi-foetal pregnancies they are quite often in a state of shock. The decision to go ahead and kill some of their own babies for the benefit of the others is not easy under any circumstances, especially in infertile couples who have tried desperately for years to achieve a pregnancy."
Julie Edwards's operation was a success. Her twins, Michael and Elizabeth, were born full-term and are now healthy two-year-olds. Does she dwell on the thought of the other children who might have been born? "Not at all. I occasionally wonder if I'd havehad more girls or more boys but I have two happy children and I want to look forward not back."
When Vivien Heath, 31, became pregnant with quadruplets after fertility drug treatment she, too, was distraught. But she could not bear the prospect of embryo reduction. "As far as I was concerned, four babies were there and we would have to make the best of it."
The quads were born at 26 weeks on Christmas Eve, 1992. Severely premature and underweight, they faced serious problems. Nathan died after two days. Kristian, Matthew and Ellis all needed major surgery and spent months in intensive care. All three have chronic lung problems. Kristian has hydrocephalus and a permanent shunt to drain excess fluid from his brain to his stomach. Cerebral palsy is also suspected, which means he may never walk.
Mrs Heath says that life revolves around the triplets: there are never enough hours in the day, and there is never enough money. "Sometimes I'm almost in tears when my husband gets home from work. Our marriage has gone through the worst period since having the triplets and we've nearly broken up two or three times."
But despite the difficulties, she says that her feelings about embryo reduction remain unchanged. "I can't honestly say I would have chosen to have any of them aborted because I look at them now and think: who was I to take your life away from you?''
Dr Richard Nicholson, editor of the Bulletin of Medical Ethics, is deeply uneasy about the process. "Embryo reduction is ethically unacceptable," he says. "Here we are, specifically creating human embryos and then somebody throws their arms up in horror and says we've got too many now, let's kill a few off. It's quite different from the circumstances of an ordinary abortion in which people are faced with the problem of a baby which is unplanned or unwanted."
The ethical problems do not end there. Most selective terminations reduce the pregnancy to twins, but ultimately the decision on how many embryos are aborted has to be left to the mother. On rare occasions, a woman insists that pregnancies are reduced toone embryo because she feels she would not be able to cope with twins.
In the United States, embryo reduction for social, rather than purely medical, reasons is far more common than in Britain. In New York, a clinic headed by Ilan Timor, professor of obstetrics and gynaecology at Columbia Presbyterian Medical Centre, has performed about 25 operations to reduce twins to a single pregnancy.
"In some of these cases, there are good medical reasons," says Professor Timor. "In others, mothers simply say they can't afford to put two kids through college. I am prepared to terminate a pregnancy, so it would be hypocritical of me to refuse to do reduce it from twins to a single baby. I do the operation, but with a heavy heart."
Dr Nicholson would like to see more public debate of the issue but is not surprised that many gynaecologists are reluctant to discuss embryo reduction openly. Some are even jumpy about how the process is described. They are keen for it to be referred to as embryo, rather than foetal, reduction - or worse still, feticide - even when performed after eight weeks. The term "selective" reduction of pregnancy is also avoided as doctors believe it has overtones of them playing God. In fact, during the operation the embryos which are terminated are those which are easiest to reach.
Since 1991, doctors have had notify the Department of Health every time they perform an embryo reduction. Yet curiously, no official figures have ever been published, unlike abortion statistics. So no one can be sure how many such operations are taking place.
Most doctors agree that embryo reduction should be a last resort and that the source of the problem lies in the type of fertility drug treatment given every year to tens of thousands of women. While all fertility treatment carries a risk of multiple pregnancy, the human gonadatrophin drugs which stimulate the ovary directly appear to be the main source of high multiple pregnancies.
Human gonadatrophins, used in the first stage of the cycle, stimulate the ovaries to produce egg follicles; in the second stage Human Chorionic Gonadatrophin is used to stimulate the ripening and release of the egg follicles. King's College Hospital has reduced pregnancies from as high as seven, eight - even 10 embryos - to twins, all caused by stimulation of the ovaries.
These drugs are prescribed not only by gynaecologists but by some family doctors. They are outside the remit of the Human Fertilisation and Embryology Authority which, in contrast, places strict controls over clinics offering treatment such as in vitro fertilisation or gamete intra-fallopian transfer, and which puts a limit of three on the number of fertilised eggs put back into the womb.
Last year, the Royal College of Obstetricians and Gynaecologists issued detailed guidelines on ovarian stimulant drugs aimed at minimising the risks of multiple pregnancy. These stressed the importance of using ultrasound during treatment to check how many egg follicles have been produced; if it looks as though many eggs might be fertilised, the second stage of treatment could be withheld, preventing the follicles from being released. Blood tests to check oestrogen levels are also recommended.
But the Royal College says it has no way of knowing what proportion of hospitals are following its advice. Indeed, some consultants have written back saying it is extremely difficult to meet the guidelines because of lack of facilities.
Vivien Heath was not given an ultrasound scan to detect how many egg follicles had been produced because of a "lack of resources" at the hospital where she was treated, although scanning has since been introduced.
Infertility treatment has given hope to thousands of couples, and new techniques are constantly being developed. But unless standards are raised in this area of treatment, many more couples may have to make an agonising choice - between having part of a multiple pregnancy aborted, or facing the potential health and social problems of having triplets, quads or more.
The writer is the BBC's health correspondent. His report for Public Eye, `Little Miracles', will be shown on BBC2 tonight at 8pm.Reuse content