'Sister effect' makes teenagers more likely to get pregnant

Teenagers are more likely to get pregnant if their sister had a child as a teenager, new research reveals.

The study of over 42,000 Norwegian teenage girls shows the probability of a younger sister having a teenage pregnancy increased from one in five to two in five, if a sibling had a child as a teenager.

The study states: ‘Sisters generally spend more time together than schoolmates or friends and so sisters are likely to be influenced by the behaviour of their siblings.’

The work, by researchers in the UK and Norway, suggests that the most likely follow in their sisters’ footsteps are those of a similar age, or a poorer background.

One of the researchers, professor Carol Propper, said: ‘Two groups were particularly vulnerable - those in low income households and sisters close in age.’

She said the ‘sister effect’ not be as strong in siblings with a larger age gap as they wouldn’t be as close and would mix in different social circles.

The research, carried out in conjunction with the University of Bristol, looked at data from children born between 1947 and 1958 to compare families from a similar background from different regions of Norway.

It also shows spending more time in school reduces the probability of a teenage pregnancy, but on a much smaller scale than the effect of a pregnant sister.

The Family Planning Association said the results are interesting but may not apply to the UK.

Rebecca Findlay, from the association, said teenage pregnancy is ‘complicated’.

‘Social and economic deprivation and poor education all impact hugely onto it and we already know that being the daughter of a teenage mother is one of the contributing risk factors towards teenage pregnancy,’ she said.

‘Although it's difficult to draw direct comparisons to this country just yet, this research is of interest.’