Family pressures and inadequate sex education stop most pregnant teenagers from even considering the possibility of an abortion, according to a report today from the Joseph Rowntree Foundation.

As the government wrestles with policies to reduce the highest rate of teenage births in western Europe, researchers from York university found a lack of support for young women having to make quick decisions when faced with an unplanned pregnancy.

They interviewed 41 young women in Doncaster, a town with one of the highest teenage pregnancy rates in England. Almost all were shocked to discover they were pregnant. There was no evidence that any deliberately became pregnant to secure economic independence or housing. By the time pregnancy was confirmed, the women had seven to 14 weeks to decide on an abortion.

They were primarily influenced by attitudes and experiences they had before they became pregnant and by the experiences of those around them.

"Anti-abortion views were prevalent and families had not discussed abortion as an option. In contrast, young motherhood was highly visible and had been discussed within families," the report said.

One young mother reported that her boyfriend's parents said an abortion would amount to "murdering their grandchild". Another said she would have been hit and abused if she returned to school after terminating her pregnancy.

The few who chose abortion said a big influence was knowing someone who had made the same decision. For some the result was isolation from their peers and open hostility. "I told a woman I worked with and she called me a murderer," said one.

Latest figures show almost 90,000 teenagers became pregnant in England in 1997, of whom 56,000 gave birth. Almost 7,700 were under 16, of whom 3,700 gave birth.

The government has set a target of halving the rate of teenage conceptions within 10 years.