Stunning 4-D ultrasound images of the foetus at 15 to 22 weeks gestation last year prompted a national debate over late-term abortion.
Newspaper reports suggested that it could "walk", "cry" or "smile" while inside the womb and that these behaviours indicated foetal experience.
Subsequently, Tony Blair was put under pressure to explore a reduction to the legal limit for abortion with David Steel, architect of the 1967 Abortion Act, calling for it to be reduced to 18 weeks.
Although 4-D ultrasound images are new, attempts to undermine the original Act with new facts about the foetus are not.
The Alton Bill of 1987, which sought to restrict late-term abortion, was supported by new findings suggesting that the foetus could dance to pop music and recognise the theme tune of his mother's favourite soap opera.
In the mid-1990s, Lord Alton tried again, this time wielding new evidence that the foetus could feel pain and would suffer tremendously when aborted.
In the US, the potential for foetal pain was a major focus of the recent court cases challenging the Partial-Birth Abortion Ban signed into law by President George W. Bush in 2003. These appropriations of science into the battle against abortion are mistaken. Pursuing a political agenda with science runs the risk of misinterpreting the facts it can provide.
There can also be no question that foetal development is amazing. In the course of 40 weeks there is progress from a barely observable ball of cells to a waking baby that can sense and observe.
But there can be no question that foetal development is limited. The neuronal function of the brain continues apace during late-term gestation and after birth, resulting in the appearance of coordinated motor movements, emotions such as stranger anxiety and advanced memory functions.
Gradually the baby develops abilities to integrate across her sensory systems, to label objects and to abandon neonatal reflex activity in favour of volitional behaviour.
Seeking an equivalence between foetus and baby, child or adult is bound to produce disappointment or exaggeration.
There is also an attempt to circumvent the true abortion battleground that places the independence and autonomy of women against that of foetal life.
For the life of the foetus to be protected it is necessary to force some women to become mothers against their will. Equally, for a woman's control over her fertility to remain intact, it is necessary for some foetuses to die at a late stage of development.
Regardless of what advances science may make there will never be a "foetalometer" to tell us when one decision is wrong and another correct.
The decision is social and political, and must be decided on legal and moral grounds, not scientific ones.
Late last year my wife gave birth to our second daughter, a very much wanted child. At 18 weeks we gazed in delight at the grainy ultrasound picture. It didn't matter to us whether our baby could feel pain, we still didn't want her harmed; it didn't matter whether she could hear, we still wanted to talk to her; and it didn't matter if she could then "walk", "smile" or "cry", as we looked forward to those things happening.
But for a woman seeking a termination the source of our excitement is her source of stress. She seeks to avoid the developmental process to avert an unhappy event.
While seemingly equivalent from a technical or scientific point of view, a pregnant woman with a wanted baby is clearly very different from a pregnant woman with an unwanted foetus.
The question of who should and should not continue a pregnancy is not one that science can resolve. Trying to do so is likely to produce both bad science and bad law.
Stuart Derbyshire
Assistant professor in radiology and esthesiology
University of Pittsburgh
He will be speaking at a seminar on late abortion in the House of Commons on January .