In 1961, at the age of 30, Diane Munday accidentally got pregnant. She already had three children under the age of four, so decided to have a termination. It wasn't an easy choice. Abortion was then illegal: the only way she could get treatment was to pay for a Harley Street doctor to certify her suicidal, at a cost of 10 guineas, and then apply for a quasi-legal abortion. This cost £90 - a lot of money in 1961.
"Already having three children," says Munday, "I knew how much it took to care for them, and it made me recognise how wrong it would be for me to have a child I could not look after properly. Having children strengthened my feelings on abortion. When you have experience of both the joys and the hard work, the stresses and strains, it has always seemed to me that children should come at a time when they're wanted."
For some people, the very idea of a pro-choice mother is offensive. Their main charge is simple: how can women speak up for legal abortion when they know what it feels like to carry a baby? This argument has been strengthened both in the UK and the US by women who have announced, after giving birth, that they have less sympathy for the pro-choice movement. After becoming a mother, the feminist author Naomi Wolf suggested abortion should be legal only up to 12 weeks. "I had something of a conversion when I was pregnant in my mid-30s with a baby we wanted," she wrote. "I found I could not square the enthusiasm my husband and I were expected to show for the wanted foetus in the adorable ultrasound ... with the casual attitude to an unwanted baby at the same stage that was the norm in debates about rights to abortion."
But many women have the opposite reaction. "I always thought of myself as pro-choice, but I was more so after I had children," says Helen McGowan, 42, a legal officer from Stockport and mother of three. "Before you have children, you don't think about the issues so much unless you've had an unwanted pregnancy, which is not a situation I was ever in."
The web is awash with pro-choice mothers defending their views. "My mother was pro-choice and she chose to have me" ... "Pro-choice does not mean pro-abortion. It means choosing!" This is a difficult sentiment for anti-abortion campaigners to understand, but I sympathise with it entirely. After having children, I too feel more strongly pro-choice, not because I feel "casual" about abortion (who does, really?) but because I definitely don't feel casual about being a mother. Now that I know how difficult it is to be a parent - especially a good one - I view choice as a right we should fiercely protect. Just because you have felt a baby kicking inside you - and you understand the enormity of carrying human life - doesn't mean that you feel everyone should be forced to go through with a pregnancy. Anyone who knows the emotional demands of being a parent should shudder at the thought of psychologically fragile women being coerced into it.
Dr Ellie Lee, a sociologist at the University of Kent and author of several studies on abortion, says there is a huge invisible army of pro-choice mothers - many of whom, like Munday, have had terminations after having children. Lee believes the debate has been skewed by the assumption that terminations are just for "feckless teenagers and rape victims".
Lisa Hallgarten, head of policy at Education for Choice, agrees there is a stereotype that abortion is something you do when you're young, "and then you get older and become a mum". The reality is, says Hallgarten, that 42% of women having abortions already have children. "One of the things the anti-choice movement like to work on is this sense that women don't really know what they're doing; that they don't realise they're killing a baby. But when you see how many women who have had abortions have had a baby, you see that is a myth. Women do it very thoughtfully and consciously - not with their eyes shut."
The website prochoicemajority.org.uk features many stories of mothers who have had terminations. They are mainly pseudonymous and often desperate, their feelings about abortion mixed. Sarah, 43, who had an abortion at 11 weeks, writes that she "had three children already and the fourth pregnancy was an accident. My relationship with my husband wasn't very stable and he felt another baby would jeopardise the family we already had." Jess, 28, who had an abortion at 20 weeks, says she has "two children already, and after each birth I suffered from terrible postnatal depression. I drank heavily and at times endangered the lives of my children." One of the most heart-stopping comments is a woman who writes that even if she "made the wrong choice, it's my choice to make".
The experience of motherhood enables many women to put themselves in someone else's shoes for the first time. Kellie O'Dowd, 34, a mother of three and women's rights activist from Belfast, says she sees "choice as a human rights issue. It's not something I have had to access myself, but I have had to arrange abortions for friends and I supported them. With three children under the age of 10, I know what motherhood entails. It's difficult enough in a supportive environment, when you're not on the breadline and you don't have mental health issues - all things that can lead women down the path towards a termination."
Johanna Payton, 35, mother of four-year-old Eliott and author of Abortion: the Essential Guide, says, "It's fantastic becoming a parent - when you're ready. As a mother, I appreciate more than ever that you need to be 100% prepared. I think we're so lucky to have a choice in this country. Knowing what it's like to feel emotionally ready to have a baby strengthened my thoughts about being pro-choice." She says that either choice - to have the baby or have a termination - can be viewed as a positive one. That's the whole point.
"There is so much difference between a wanted pregnancy and an unwanted one. I had a pregnancy scare last year and found myself thinking I was more than happy with one child. Having gone through a difficult pregnancy, a difficult birth and the first year of having a baby, I can appreciate how hard it is. Becoming a mother is wonderful - when you really want to. Not when it's forced on you".