Teenage pregnancy are “contagious”, according to a study which has found that younger sisters tend to follow the example set by their older siblings.When an older sister becomes a gymslip mum, the younger sister is twice as likely to do the same.
This “peer effect”, as Bristol University researchers called it, raised the chances of becoming a teenage mother from about one in five to two in five.
The effect was stronger when sisters were closer together in age, while it was also stronger in poorer households.
Being educated to a higher level decreased its effect, but the research found that the sibling effect “dwarfs” that of more years in school.
Professor Carol Propper said: “Previous research has shown that family background and raising the education of girls decreases the chances of teenage pregnancy.
“However, these findings reveal the positive sibling effect still dwarfs the negative effect of education. These findings provide strong evidence that the contagious effect of teen motherhood in siblings is larger than the general effect of being better educated.
“This suggests that more policies aimed directly at decreasing teenage pregnancy may be needed in order to reduce teen births.”
The analysis was based on census data from 42,000 Norwegian women born after the Second World War. Most gave birth in the 1970s and 1980s.
The study, a collaboration with academics at Bergen University in Norway, the Norwegian School of Economics and Imperial College London, has been published as a working paper by Bristol University’s Centre for Market and Public Organisation.