"Teenagers should not allow themselves to get into situations where they even need to consider having an abortion. The only time it is right to have a child is in a stable relationship, when you can support your child both financially and emotionally. Unless you are at that stage, you should be careful and not get yourself pregnant. Otherwise you are just being irresponsible and selfish."

Are these the words of a right-wing leader writer? Or a pro-life organisation spokesperson? You would be wrong to assume either was the right answer. This is the opinion of Victoria, a 14-year-old schoolgirl from London. Teenagers are not meant to talk like this, at least not according to the well-rehearsed national debate over teenage pregnancy. Even adults prepared to credit teenagers with maturity in taking decisions about reproduction may assume that school-aged sex is free and easy, and the possibility of creating life considered in a cavalier fashion, if it is considered at all.

So the findings of a new study published this week will come as a surprise to many. The survey, by the Joseph Rowntree Foundation, talked to 41 young women in Doncaster who had become pregnant at a young age and, in the vast majority of cases, continued with the pregnancy to full term. It found that almost all had been shocked to discover they were pregnant. They were not trying to please their boyfriends, and most took the decision on whether or not to keep their baby without much reference to the child's father.

Most tellingly, they were far from irresponsible. In fact, the teenagers were so convinced of the need to take responsibility for their own actions that terminating the pregnancy was not an option considered. Getting pregnant may be frowned upon by the moral majority, but even the report's authors confessed to surprise at the force of moral disapproval displayed by girls towards their peers who had had abortions.

What would happen if everyone at school knew that someone had had an abortion? "You wouldn't be able to go to school," replied one girl. "You would get called names. You would probably get hit and all."

One teenager, Lucy, had decided not to continue with a pregnancy. "I told this woman I knew who I worked with and she turned round and called me a murderer."

The strength of feeling against abortion on the Doncaster housing estates where these women were interviewed surprised Sharon Tabberer, one of the researchers. "They said it was nothing to do with religion, but that it was 'wrong'. It just wasn't something that people like them did."

"What is so interesting is this incredible difference when it comes to social groups and abortion," says Anne Weyman, chief executive of the Family Planning Association. "Middle-class girls, we know, are less likely to get pregnant than less well-off girls, but they are also much more likely to have abortions. The two groups just don't have the same sort of views.

"It is interesting that in a group of young women who have less control over their lives than other young women, that is being reinforced by the fact that they feel abortion is not an option for them either."

So how did we get to the point where only well-off, well-educated girls tend to consider termination? Education on family planning and sexual health simply tries to sweep abortion under the carpet, argues Weyman. "There has been a real reluctance to consider that abortion is an important option for young women, and to make sure that it is offered to them. Everything is about prevention - which is good - and support for new parents - also good - but there is nothing about the choice you can make in the middle of these two options."

She points out that government guidelines on sex education have not, until this year, included a recommendation that girls be given advice on terminations. The DfEE's advice, published in June, tentatively suggested that "young people need to be aware of the moral and personal dilemmas involved in abortion and know how to access a relevant agency if necessary".

By "relevant agency" it may be assumed that the department means impartial advice on termination - but even couched in such language the recommendation attracted howls of protest from the pro-life lobby.

There is little doubt that the Doncaster study teenagers are aware of the troubled morality involved in abortion. "It was about taking responsibility for their actions," says Tabberer. "They said things like: 'It was me who made the mistake and why should the baby have to suffer? I didn't use protection, it's not the baby's fault.'"

James is 19 and already the father of a one-year-old son. While he does regret his role in the pregnancy, he is convinced of the importance of taking responsibility for creating a life. "It happened, and now I have a responsibility to my child. It is difficult trying to bring up a baby on my own, they are expensive and it limits the things I can do in my life. But it is not me that is important any more, my child is my priority."

"In this country we have a very censorious view about the unwanted consequences of sexual activity," says Weyman. "It makes young people believe that, well, I've had sex, so I have to live with the outcome. It's a lack of being able to say, well I do have a choice."

For teenagers who do decide to have an abortion, the decision is tough, argues 16-year-old Aisha. "When I realised I was pregnant, I just cried and cried and cried. It's like, when you're young, you dream about having children and being with someone you love, and all that is taken from you in 10 minutes and a pregnancy test."

Aisha lives in London and is at college taking A-levels. "Having an abortion was the hardest thing I have ever had to deal with, and I don't think there can ever be anything worse. Some people are like, how can anyone kill their child? That's how I felt about myself, afterwards, but it wasn't like that. I'm 16, I couldn't support a little child financially, and I wasn't ready emotionally. How could I bring a life into this world when I knew it would suffer."

Aisha explains that her background made the decision even more difficult for her. "For any daughter to tell her parents she is 15 and pregnant is hard. But when your parents follow traditional Indian beliefs and are obsessed with keeping the family name respectful ... at least some people have their families support when they have abortions, I had nothing."