A new study [1] has suggested that teenage motherhood is ‘contagious’ within families. Researchers from Bristol 
University found that the sister of a teenage mother is twice as likely to follow in her footsteps as a girl with no family experience of early motherhood.
And the ‘peer effect’ on girls aged 16 to 19 was shown to have a far more powerful impact than any education or advice they are given at school. The closer the sisters were in age, the more powerful the effect was.
The figures may help to explain why the British government’s Teenage Pregnancy Strategy has been largely a failure. Despite a £280million investment and a much-trumpeted advertising campaign to promote contraception, Britain still has the highest teenage pregnancy rate in Europe, six times higher among girls under-16 compared to Ireland.
Figures released by the Office for National Statistics in February showed that in 2009 – the most recent year for which there are records – the rate of conception among UK women under 18 was 38.3 per 1,000 girls, only 17 per cent down from 46.6 in 1998.
Researchers studied census figures from 42,606 women in Norway in the 1960s, as its data is unique in linking teenage pregnancy with family relationships.
The study found that if a girl became a teenage mother, the probability of her nearest younger sister doing the same increased from a one-in-five chance to two in five.
Higher education levels and a more affluent family background have tended to lower rates of teenage pregnancy in developed countries.
But Professor Carol Propper, who led the study, said: ‘These findings provide strong evidence that the contagious effect of teen motherhood in siblings is larger than the general effect of being better educated.
‘The message is that what you do in school is not enough to counteract the effect of siblings, and that needs to be accounted for in public policy. It needs to focus more on what’s going on in families.’
The study supports previous research showing younger children in families are influenced more by the sexual behaviour of their older siblings than that of their friends.