Nearly a quarter of teenagers in England and Wales who have had an abortion have been pregnant before, according to new research from the University of East Anglia (UEA).

Drawing on more than 20 years' worth of data the study shows, for the first time, the number of young women aged 15-19 undergoing an abortion who had experienced at least one previous pregnancy, resulting in either a birth - live or stillbirth - or abortion.

The researchers analysed national abortion figures for England and Wales from 1992 to 2013, published by the Office of National Statistics and the Department of Health. They aimed to more precisely estimate the number of teenagers having an abortion who have had one or more previous pregnancies. Earlier studies have reported the number of previous pregnancies or abortions, but have not been able to account for the proportion of young women who experienced both.

In 2013, approximately 23 per cent of teenage women having an abortion had been pregnant before. A minority, less than five per cent, had two or more previous pregnancies, though this number almost doubled between 1992 (937) and 2002 (1823).

During the period studied, the number of teenagers having an abortion as a result of a subsequent pregnancy increased by 33 per cent, from 5260 in 1992 to 6631 in 2013. Most of this increase took place before 2004 and the figure appears to have stabilised. The number peaked in 2008, when 9834 had experienced a previous pregnancy.

Published in the Journal of Adolescent Health, the findings show that teenagers who become pregnant are at a higher risk of further pregnancies in their teenage years. While the teenage conception rate in England and Wales has declined in recent years and is now at a record low, further reductions are still needed to bring it in line with other western European countries.

The authors say that in order to do this efforts need to focus not just on preventing first-time pregnancies but also to support pregnant and parenting teenagers to better manage their reproductive lives. They call for greater emphasis to be placed on developing more sophisticated and effective interventions to prevent future unplanned pregnancies among this group, such as helping the young women to find a contraceptive method that best suits them, making it easy for them to obtain this and providing ongoing support.

Lead researcher Lisa McDaid, of the School of Health Sciences, worked with colleagues Prof Jacqueline Collier of the School of Psychology and Prof Mary Jane Platt from UEA's Norwich Medical School. Ms McDaid said that as not all teenage conceptions are first-time conceptions, it had been important to accurately identify the number of teenagers who become pregnant for a second time or more.

"This information will help to guide more targeted interventions to continue the downward trend in pregnancy and to monitor the effectiveness of current sexual health priorities on reducing conceptions and unwanted pregnancies among this age group," said Ms McDaid.

"The continuing high proportion of teenagers who have an abortion following one or more previous pregnancies highlights the complexity of these young women's lives and we need to recognise that the circumstances of each pregnancy may be very different. Our results clearly demonstrate that young women who become pregnant can be considered a high-risk group for subsequent, unplanned, mistimed, or unwanted pregnancies, emphasising the importance of embedding preventative actions and behaviours among this group after a birth or abortion."

In 2013 responsibility for commissioning community contraceptive services moved from the NHS to local authorities, while maternity and abortion services are the responsibility of NHS Clinical Commissioning Groups. Ms McDaid said this separation could make it harder for teenagers to access support and contraception when they most need it.

"All organisations will need to work together so that teenagers have an effective contraceptive plan in place that meets their needs after a pregnancy, along with receiving ongoing support to encourage up-take and continuation, and improved access to emergency contraception," said Ms McDaid.

The research builds on a previous study conducted by Prof Collier, who said further work was still needed to establish a more accurate and comprehensive picture of subsequent teen pregnancies and their patterns according to the outcome of the pregnancy.

"The teenage years are a unique time where a number of different changes and challenges are faced," said Prof Collier. "In-depth work to explore teenagers' experiences of subsequent pregnancies and the factors that influence their sexual and contraceptive behaviours is needed to increase understanding of the complexities of the issues involved."

'Previous pregnancies among young women having an abortion in England and Wales', Lisa McDaid, Jacqueline Collier and Mary Jane Platt, is published in the Journal of Adolescent Health.