The findings come from one of the first studies investigating school-age parents who choose deliberately to have children, rather than those who have unplanned pregnancies.
Researchers at the Trust for the Study of Adolescence concluded that it was difficult to estimate what proportion of teenage pregnancies are planned but suggest the practice is more common than is widely believed. They interviewed 41 teenage mothers and 10 teenage fathers about their decisions to have a baby between the ages of 13 and 19.
Some of the reasons given by the fathers were different to those given by the mothers, although they both tended to come from disadvantaged backgrounds.
"The vast majority of (male) interviewees did not have a steady 'father figure' when they were growing up, and most said this had affected their decision," the report said. "They wanted to be a better father. This was the reason most explicitly linked to planning a pregnancy."
The researchers quoted a teenager, now aged 19, who said he felt lucky to be a father because he had always believed he would be a good parent. "I didn't have a dad, so I wanted to see if I could do it and give my son more than what I had, really," he said.
The researchers found that the degree to which the teenage girls had consciously planned to be a mother varied.
They were split between those who decided with clear support from their boyfriends, those who had a limited discussion with their boyfriends, those who did not involve their boyfriends at all and those who were "positively ambivalent" about whether they became pregnant or not.
There were also some mothers who chose to have babies for specific reasons, including fear of not being able to have a baby or, in several cases, guilt after a previous unplanned pregnancy ended in miscarriage. The report suggested that many mothers decided to give up contraception and place the prospect of pregnancy in the "lap of the gods" because they did not realise how likely it was.
"'Planned' teenage pregnancy: views and experiences of young people" is in Education and Health, Volume 24, Number 3