NEW YORK - Young women whose high school friends have had a baby are more likely to follow suit, according to a new study.
Researchers saw the effect among young US women who planned their pregnancies, but the childbearing choices of friends seemed to have no impact on the number of unwanted pregnancies.
"In our study we focus on high school friends because the later a friendship is formed, the more likely it is that the individual chooses the friends on common future family plans or common family orientations," Nicoletta Balbo told Reuters Health in an email.
Balbo, a researcher at the Carlo F. Dondena Center for Research on Social Dynamics at Bocconi University in Italy, coauthored the study with Nicola Barban, a sociologist at the University of Groningen in the Netherlands.
"We looked at dyads (pairs) of friends to see whether the childbearing of one of the friends in the dyad increases the probability for the other friend to have a child," Balbo said.
The researchers analysed data from a large US study that has followed thousands of participants, starting when they were adolescents in the 1990s, and doing repeated interviews over the years.
Balbo and Barban focused on 1,170 women, of whom 820 became parents during the study period. About half of the pregnancies were planned and half unintended, according to the women's own reports. Their average age at the time they had their first child was 27.
The researchers found that 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 said there are three possible mechanisms by which a friend may influence another friend in her decision to have a child.
"The first mechanism that might be at play is the so-called social influence," she said. "We all compare ourselves to our friends and being surrounded by friends who are parents makes us feel pressure to conform to parental status as well."
The second potential mechanism Balbo cited is social learning. "Friends are an important learning source," she said. "Becoming a parent is a radical change in an individual's or a couple's life, and by observing our friends, we can learn how to fulfil this new role and therefore be more willing to become parents."
Balbo added that cost-sharing dynamics might be at play as well, and having children at the same time as friends may bring about many advantages.
"For example, we can share the childbearing experience and thus reduce the stresses and costs associated with pregnancy and child rearing," she said. "In contrast, being the only childless couple within a group of friends who have children can lead to isolation."
The authors only looked at the association with first-borns, they didn't study any effects on subsequent births, nor did they look at the impact wider groups of friends might have.
Laura Bernardi said that one other possible explanation for the increased likelihood of having a baby may be the exposure to and interaction with small children.
Bernardi, who is deputy director of the National Center of Competence in Research LIVES programme and a researcher at the University of Lausanne in Switzerland, was not involved in the new research. But she has studied the effects of social networks on childbearing and found similar results.
Bernardi said the methods used in the study are appropriate, though not taking larger social networks into account may have limited the study because these friendship dyads don't typically occur in isolation - young women usually have several friends.
"The potential influence of one friend having a child while all other friends are childless and of having a cluster of friends having a child at the same time is very different," Bernardi said.