The emotive photographs, taken with new fourdimensional imaging technology, have created a misleading impression that foetuses become viable and potentially self-aware at a much earlier stage than is actually the case, according to experts on foetal development.

The 4-D scanning technique, developed by Stuart Campbell, of the Create Health Clinic in London, has helped to revive abortion as a political issue since he published his first images two years ago.

The pictures showed foetuses of 12 weeks’ gestation, bouncing and kicking in the womb, before the mother is usually aware of such movement. At 16 weeks, they can be seen sucking thumbs and yawning, and at 18 weeks opening their eyes.

Although Professor Campbell insisted that the images did not mean that the foetal brain was consciously controlling these movements, they were seized on by anti-abortion campaigners to demand a reduction in the time limit on terminations. At present, abortion is allowed until 24 weeks of pregnancy, except in the case of severe foetal abnormalities or danger to maternal health. The 4-D scans of much younger foetuses, along with advances in treating premature babies that allow a few to survive births as early as 23 weeks, have led to calls for that limit to be cut.

The Archbishops of Canterbury and Westminster have both said that the law should be revisited. Michael Howard, the former Conservative leader, said last year that he would back a 20-week limit, and Tony Blair is also thought to support a review.

Doctors and researchers, however, said yesterday that the images had confused the public about the real state of the science.

“I had two reactions when I saw those photographs,” said Donald Peebles, of the Department of Obstetrics and Gynaecology at University College London. “One was that this was a fantastic piece of technology that showed very clearly what we knew already about the foetus in a way that was comprehensible to the public.

“But there was also a temptation to associate these movements — sucking a thumb, gasping as if talking — with adult movements, to think it is sucking its thumb because it is happy. It’s that feeling which I think is extraordinarily dangerous.”

Though the foetus clearly looks human by 12 weeks, proper sensory development takes place much later, he said. There was a risk that the pictures would make people assume that foetuses have more advanced brains than is the case.

“The neurons in the brain might be in their final positions by about halfway through the pregnancy, but that in no way means they function in an adult way. These images don’t tell me anything I haven’t known for 30 years with ultrasound scans. We know what it looks like, and that it moves continuously. I don’t think in a scientific sense this sheds any new light on the debate.”

Huseyin Mehmet, Reader in Developmental Neurobiology at Imperial College London, said: “Personification of the foetus at that age is dangerous. Scans that look at the structure of the foetal brain at 23 to 24 weeks show that the human brain is extremely immature. It is the period between 24 and 40 weeks that is largely responsible for brain development. I was worried when I saw those images. To suggest that an early foetus in utero has those kind of human qualities of being able to suck its thumb and move, that it meets the biological definition of being really viable outside the uterus, is very difficult indeed.”

John Watts, Professor of Neonatal Paediatrics at University College Hospital in London, said. “It is clear that a vast amount of activity is happening mainly in the last three months of pregnancy. We will never know at what point foetal consciousness and awareness start. But the link between cortex and the rest of the body doesn’t come into play until 23 to 24 weeks, when the first connections are created.”

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