MPs have voted to retain 24 weeks as the upper time limit for abortions. But what are the issues in the debate and how has the law changed over the years?
Where does the current law stand?
A private member's bill brought by David Steel MP led to the Abortion Act 1967, which is still the law governing abortions in England, Scotland and Wales.
Technically the law did not legalise abortions, but rather provided a legal defence for those carrying them out.
Abortions can legally be performed under certain conditions - the first is that continuing with the pregnancy involves a greater risk to the physical or mental health of the woman, or her existing children, than having a termination.
The woman's "actual or reasonably foreseeable future environment" may be taken into account.
Abortion up to 24 weeks is also allowed if there is a substantial risk that the child when born would suffer "such physical or mental abnormalities as to be seriously handicapped".
An abortion must be agreed by two doctors (or one in an emergency) and carried out by a doctor in a government-approved hospital or clinic.
Does the law apply in Northern Ireland?
The Act does not extend to Northern Ireland, where the law has been less clear. Many women travel to England or Scotland for abortions.
A Court of Appeal ruling in October 2004 ordered the Department of Health to draw up guidelines on when abortions can be carried out under existing law, following a campaign by the Family Planning Association.
Currently, abortion is only permissible in Northern Ireland where the mother's life is in danger or there is a serious threat to her mental or physical health.
Has the 1967 law ever been updated?
Yes, via the Human Embryology and Human Fertilisation Act 1990, which was brought in primarily to control new infertility treatments and to monitor experiments on embryos.
A section of the Act also lowered the legal time limit for abortions from 28 to 24 weeks, which is now the accepted point at which a foetus is "viable".
The Act also clarified under which special circumstances abortions could be carried out at a later stage.
Abortions after 24 weeks are allowed if there is grave risk to the life of the woman; evidence of severe foetal abnormality; or risk of grave physical and mental injury to the woman.
What is happening now?
MPs were asked to vote on cutting the limit for the first time since 1990. The votes were on a series of amendments to the Human Fertilisation and Embryology Bill.
There were calls for a reduction to 12, 16, 20 or 22 weeks.
What was the argument in favour of reducing the limit?
Those in favour of a change said babies born at 24 weeks were increasingly likely to survive, and it should therefore not be permitted to abort pregnancies at this stage. Right-to-life groups add that efforts should be made to save every life.
And what was the argument against?
Studies, including one published in the British Medical Journal this month, show that while survival rates have increased significantly for babies born at 24 and 25 weeks, they have not risen for babies born 23 weeks or less. Very few terminations take place at this stage of pregnancy, but those in favour of keeping the limit as it is say that it is often the 20 week scan which reveals severe abnormalities.
Where do the three main political parties stand?
The Labour, Conservative and Liberal Democrat parties all consider the issue to be one on which individual MPs should have a free vote. Labour leader Gordon Brown says he backs sticking with the 24-week limit. Conservative leader David Cameron favours a cut.