A study conducted on more than 42,000 Norwegian girls turned up some somewhat surprising results. Apparently, you can catch a baby; or at least you can in Norway. And especially you can if you've got a sister who's had a baby.

We've all heard the old saw: "Babies having babies is contagious." And studies show that if a woman has a baby in her teens, chances are high that her daughter will, too. But what about sisters? It turns out the chances of a younger sister having a baby as a teen double, from one in five to two in five, if the older teen sister gets pregnant. But only if they're close in age. How crazy is that?

“Teenage pregnancy is complicated,” said Rebecca Findlay, from the Family Planning Association. “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. Although it's difficult to draw direct comparisons to [the UK] just yet, this research is of interest.”