The issue of foetal pain is being highlighted by anti-abortionists. But its implications extend beyond their agenda - to the process of birth itself. Rob Stepney reports
Giving a blood transfusion in the womb is the only way of saving the life of an unborn baby with severe anaemia. A doctor pushes the hollow transfusion needle into the mother's abdomen, through the placenta, and straight into a vein in the tiny liver. Ultrasound scans recorded on video show how foetuses respond.

"At least from the age of 20 weeks onwards, they move all over the place, arms and legs waving as they try to get away from the needle," says Professor Nicholas Fisk, of Queen Charlotte's Hospital, London, who has pioneered such life-saving procedures in the womb. Are those foetuses feeling pain, or are they taking only reflex-avoiding action?

In the bitter struggle between those who favour a woman's right to choose, and those who consider abortion an evil, this question is proving a crucial battleground. A Panorama programme, soon to be screened to mark the 30th anniversary of the Abortion Act, is said to make great play of the suffering potentially caused to foetuses by terminations carried out close to the legal limit of 24 weeks.

The issue of foetal pain looks set to be exploited by the "pro-lifers", especially in the run-up to the election - even though 90 per cent of terminations take place before 13 weeks, when doctors agree it is simply not an issue. But the implications extend well beyond this highly emotive area. If foetuses really can feel pain, then surgeons operating on them in the womb will want to ensure adequate analgesia. And whether the long trauma of birth itself should be accompanied by pain relief for the baby as well as the mother becomes a real question.

During vaginal delivery, each contraction rams the baby's head against the opening in the pelvis until it is squashed into a shape that will pass through. One in 10 babies are born with the additional aid of forceps, or a vacuum sucker to help drag them by the head through the birth canal. "There could be a good argument for this being painful," says Professor Fisk. The same is true of the responses he sees during foetal surgery.

Clearly we cannot ask the foetus what it feels. But Professor Fisk believes that we can understand more about what it is experiencing by measuring how the foetal hormones and brain blood flow react to stimuli that we would find painful.

With a grant from the Wellbeing charity, he is now midway through a programme of research that will shed light on this important area. Small amounts of blood taken from a 20-week foetus at the time the transfusion needle enters the liver show that levels of the stress hormone cortisol double and levels of the body's own pain-relieving opiate chemicals increase six-fold. There is also a highly significant increase in blood flow in the brain of the foetus.

Despite such evidence of a physical stress response, some doctors are convinced that foetal pain is a complete non-issue. "Foetal pain is a misnomer at any stage of foetal development," Dr Stuart Derbyshire, formerly of Salford's Hope Hospital, and now at the University of Pittsburgh, has argued. His certainty is based on the belief that the experience of pain requires not just unpleasant sensations but also emotional and cognitive components that are simply not present in the unborn baby. It is a mistake to say that biological development is enough, he claims.

A quite different view is taken by Dr Vivette Glover, a senior clinical scientist at Queen Charlotte's. "I disagree with the idea that you need any cognitive ability or prior experience to have a simple feeling of pain," she says.

It is accepted that an organism must be conscious to feel pain, and evidence from studies of people who have suffered brain injury suggests that the cortex of the brain must be functioning for anyone to be conscious. So when is the cortex of the foetus all wired up and working?

Around 24 weeks is the earliest age at which premature babies survive. At this stage of development, the cortex is "lit up" in terms of its electrical activity. But because we cannot record from the baby still inside the womb, we do not know whether there is activity in the cortex before this point.

"The earliest time at which a foetus might possibly feel something is 14 weeks," says Dr Glover. "That is when the first nerve fibres from the outside world arrive at the cortex. These are not themselves pain fibres, but in the adult they are involved in the fight or flight response, so they might mediate distress.

"Between then and 24 weeks or so, when all the anatomical pain pathways are in place, is a grey area. But until we know more, and taking the mother's well-being always into account, we should be giving the foetus the benefit of the doubt."

It is startling to recall that as recently as 10 years ago doctors did not give pain relief to new-born babies undergoing surgery. The assumption was that they did not feel pain. "Now it would be unethical not to give analgesia even to a premature baby of 26 weeks," says Professor Fisk. "When women ask us whether a foetus of the same age having surgery can feel pain, the traditional answer has been `No'. But we have a duty to find out if this is true."

This is especially so in the light of growing evidence from animal studies that stress experienced as a foetus can affect long-term development of the nervous system and sensitivity to pain. There is no certainty that this is the case with the human foetus. But we do know that one effect of circumcision in the first week of life is to increase response to pain six months later. Research from Montreal shows that immunisation causes a far longer period of crying in boys who have been circumcised than in those who have not.

The Queen Charlotte's team is now trying to discover whether the stress response in foetuses undergoing surgery can be reduced by giving a pain- killing drug such as fentanyl. Even if it were certain that the mature foetus felt pain, doctors could not give analgesia without establishing first that it was effective and secondly that it was safe.

Fentanyl is a narcotic agent. To give it to the mother in concentrations that would cross the placenta risks interfering with the mother's breathing, and whether it is practical and safe to give it to the foetus has still to be proved.

This cautious approach to pain relief during foetal surgery is backed by Peter Hepper, director of the Foetal Behaviour Research Centre at Queen's University, Belfast. But the question of pain relief during a late termination is different. Here there is no question of analgesia doing long-term damage. "In my view," he says, "the person who suffers most from abortion is the woman. And if pain relief for the foetus becomes practical, she should be the one to choose whether or not it is given."

Accepting the reality of foetal pain should not contradict a woman's right to choose, most doctors involved in this area would argue. "But people's attitude towards termination often colours their attitude to the subject of foetal pain in general. This seems wrong," says Dr Glover. "People on both sides of the abortion debate can agree that the aim is to cause as little suffering as possible".

What the foetus does and when

7 to 8 weeks Beginnings of spontaneous movement

8 to 14 weeks Reflex reaction to touch, starting with the lips and spreading to rest of body

13 weeks Electrical activity seen in the lowest part of the brain (brainstem)

20 to 24 weeks Foetus moves in response to loud noise. Physical stress response to stimuli we feel as pain.

24 weeks Electrical activity in cortex. All anatomical pathways needed to feel pain are in place. Many healthy premature babies survive

40 weeks Full-term birth