A new study found that getting pregnant is contagious among High School friends.

You've heard on yawing and other diseases being contagious, but have you ever heard of a contagious pregnancy? It's true! According to the findings of a new study, having children is contagious among high school girl friends as they enter into early adulthood.

"The study shows the contagion is particularly strong within a short window of time: it increases immediately after a high school friend gives birth, reaches a peak about two years later, and then decreases, becoming negligible in the long-run," said co-author Nicoletta Balbo from Bocconi University in Italy in a press statement. "Overall, this research demonstrates that fertility decisions are not only influenced by individual characteristics and preferences, but also by the social network in which individuals are embedded. In addition, it shows that high school friends impact our lives well after graduation."

The study was conducted on more than 1,700 American females who were 15 years old at the start of the study. All participants were followed till they reached age 30. During this time, researchers noted the impact of female high school friends on the birth of first children. They found a significant influence, even in the cases of planned pregnancies.

Researchers said that there were three main reasons that explained this influence in a better manner. Firstly, individuals, especially girls, tend to compare themselves to their friends. Hence, being around friends who have become parents increases the pressure of having their own kids. Secondly, friends are an important learning source and observing friends can help people better understand their role as parents. Thirdly, having a child at the same time as a friend comes with many advantages. Women can share the child-bearing experience together, which reduces stress.

"It takes time to have a child -- because there is a natural period before conception and because the desire to have a child develops over time," she said. "As a result, the effect of a friend giving birth is not immediate. If we had observed an immediate effect, we would have concluded that, rather than being influenced by each other, friends just decide to have children at the same time."

The study was published online in the journal American Sociological Review.