LONDON (AP) -- Human fetuses cannot feel pain before the age of 24 weeks, a British medical association said Friday -- delivering a setback for anti-abortion activists campaigning to lower the country's 24-week time limit.

Lawmakers who were considering lowering the limit to 20-22 weeks had commissioned the study by the Royal College of Obstetricians and Gynecologists.

Citing evidence from medical research and post-mortem reports, the group said nerve connections in the brain were not sufficiently formed to allow pain perception until after 24 weeks, and that even after 24 weeks, the fetus was in a state of sleep-like unconsciousness or sedation.

"There was fairly good evidence that the pathways necessary to feel pain really just aren't there before 24 weeks -- although they very clearly are there after," said Richard Anderson, a professor in human reproductive sciences with the University of Edinburgh, who was part of the study.

Some doctors disagree with the findings, arguing that fetuses can experience distress by the age of 20 weeks. The U.S. state of Nebraska recently passed a bill banning abortion at and after 20 weeks of pregnancy.

But the American College of Obstetricians and Gynecologists has said it knows of no legitimate evidence that shows a fetus can experience pain. It said a fetus' brain begins its final stage of development between the 20th and 40th weeks of pregnancy, and that certain hormones that develop in the final trimester also must be present for it to feel pain. It's not known exactly when those hormones appear.

In Britain, the Abortion Act of 1967 allows surgical abortions up to 24 weeks. A woman can still abort her baby after 24 weeks if doctors agree the mother's life is in danger or there is strong evidence that the fetus would be born with a severe disability.

The law, however, does not extend to religiously conservative Northern Ireland, where abortions are still banned unless a woman's life is in danger or at mental or physical risk. As a result an estimated 1,400-2,000 women from the British territory travel annually to England or other European Union nations to end their pregnancies.

"We have no real evidence because the unborn baby can't speak," said Bernie Smyth, director of Precious Life, an anti-abortion group active in both Northern Ireland and the Republic of Ireland. "The fact is babies have been born at 24 weeks, they have survived, and they do feel pain."

Prime Minister David Cameron had backed reducing the limit to between 20 and 22 weeks before he came to power in May. The House of Commons voted in 2008 to keep the existing limit, and Cameron's office issued a statement Friday saying no changes were planned in the policy. It said the prime minister would be led in his decision by science.

Campaigners against abortions said the report's conclusions were not definitive and did not change their view that terminating pregnancies is wrong.

"Performing abortion humanely does not justify the fact that you are terminating a human life," said Josephine Quintavalle of the London-based Comment on Reproductive Ethics.

But supporters of the current abortion laws said the findings would reassure women considering a late-term termination.

"It is vitally important to protect a woman's right to access abortion services, and British law rightly recognizes this principle," said Tony Kerridge of the sexual health charity Marie Stopes International. "The findings should give comfort and reassurance to any woman who finds herself in the extremely distressing position of having to make the decision to terminate a pregnancy at a later gestation."

The charity said late abortions were extremely rare in Britain. Last year there were fewer than 3,000 abortions above 20 weeks gestation, Kerridge said.

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