A study coauthored by Bocconi University’s Nicolleta Balbo and University of Groningen’s Nicola Barban has unearthed a potential new contagion: babies.

The Chicago Tribune reports on the study of women’s friendships and potential child birthing saying,

…After one of the women in each friendship pair had a baby, the likelihood that her friend would also have her first baby went up for about two years, and then declined.

Balbo and Barban focus on high school friends, analyzing 1,170 women in a longitudinal study beginning in the 1990s. During the study, 820 of the participants became parents, having their first child at an average age of 27.

Balbo identifies three mechanisms that might contribute to the seemingly significant amount of influence between friends. First, she discusses social influence. This hinges on the idea that we constantly compare ourselves to people around us, including friends, and may be pressured to conform to their behavior. The second mechanism Balbo proposes is social learning. Watching a friend go through parenthood may arm prospective parents with knowledge and make them more comfortable fulfilling the parent role themselves. The third mechanism focuses on cost-sharing dynamics. Being in a similar life circumstance with friends can help reduce both costs and stress.

The study has been critiqued for not incorporating larger social networks and assuming that friendships can be studied in dyads.  Either way, I’ll think twice the next time I find a baby shower invitation in my mailbox!