Originally published 2018-11-05.
Pregnancy is not literally contagious, but the decision to have a baby can spread among friends. A well-known study of more than 1,700 American women found that when a high school friend had a child, a woman's own chances of having her first child rose straight away, peaked about two years later, and then faded. The effect showed up only for planned pregnancies, which suggests that friends shape our choices about when to start a family, not that babies simply "happen" in groups.
So if your social media feed suddenly fills with baby announcements and you find yourself thinking about your own plans, you are not imagining it. Here is what the research found, why friends may influence each other in this way, and what the study does not tell us.
The study behind the headline
The research, titled "Does Fertility Behavior Spread among Friends?", was carried out by Nicoletta Balbo, then a postdoctoral fellow at the Dondena Centre for Research on Social Dynamics at Bocconi University in Milan, and Nicola Barban, then a postdoctoral fellow in sociology at the University of Groningen in the Netherlands. It was published in the June 2014 issue of the American Sociological Review, the journal of the American Sociological Association.
The authors used the National Longitudinal Study of Adolescent Health, usually called Add Health, a long-running US survey that began with teenagers at school and followed them into adulthood. Because students were asked to name their friends while still at school, researchers could later compare when each woman had her first child with when her named friends had theirs. The sample included more than 1,700 women, followed from at least age 15 to about age 30. Their median age at first birth was just over 27.
What the researchers found
- A friend's baby raises your own chances. After a high school friend gave birth, a woman became more likely to have her first child too.
- The effect follows a curve. It started immediately, reached its peak about two years later, and then fell away until it was negligible in the long run.
- It applies to planned births only. The link held for intended pregnancies, not unplanned ones, which points to deliberate decisions rather than chance.
- It was new evidence. According to the authors, earlier research had looked at similar effects among relatives and coworkers, but this was the first study to show it among friends.
The two-year delay is one of the most interesting parts. As Barban explained, it takes time both to decide you want a child and to conceive one. If friends had all had babies at exactly the same moment, that would suggest they had simply made similar plans in parallel. A lag fits better with the idea that one friend's experience nudges the other.
Some reports of the study added further figures, such as the number of pregnancies in the sample or the share that were planned. Those figures do not appear in the published summaries of the study, so treat them with caution.
Why friends influence each other's family plans
The researchers suggested three main reasons, each easy to recognise from everyday life.
1. Comparison and gentle pressure
We measure our own lives against people our age. When close friends start becoming parents, it can raise the question "what about me?", and conversations, family members and social events can all add a little extra pressure.
2. Learning by watching
Becoming a parent is one of the biggest changes in a person's life, and it is full of unknowns. Seeing a friend go through pregnancy, birth and the first months with a baby turns an abstract idea into something real. You see what the sleepless nights look like, but also the joy, and you learn practical things that make the step feel less frightening.
3. Sharing the journey
Having children at the same time as friends has obvious advantages. You can swap advice, hand-me-down clothes and babysitting, and your social lives stay in step. The authors noted that this can ease the stresses of pregnancy and early childhood and make it easier to keep the friendship going through a period when many friendships drift.
What the study does not show
It is easy to turn a study like this into a catchy line, but some caution helps.
It is about timing, not destiny. The research shows that friends' births are linked to the timing of first births. It does not show that anyone has a baby only because a friend did, or that people without children are somehow resisting a trend.
It looked at one group. The sample was American women and their female high school friends, in a particular generation. Men, older friendships, other countries and other cultures may show different patterns.
Similar people make similar choices. Friends often share backgrounds, values and life stages. The researchers tried to separate real influence from these shared circumstances, and the delayed effect supports the idea of influence, but no observational study can rule out every alternative explanation.
Influence is not a bad thing. As Balbo's work suggests, decisions about children are shaped by the people around us as well as by our own preferences. Plenty of people see friends become parents and still choose a different path or a different time, and that is just as valid.
If a friend's pregnancy has you thinking
A friend's news can stir up all sorts of feelings: excitement, longing, worry or even a sense of being left behind. A few things can help:
- Ask yourself what you actually want, separate from what everyone else is doing. A friend's timeline is not a deadline.
- Talk openly with your partner, if you have one, about hopes, finances, work and support.
- Use your friend as a source of honest information. Most new parents are happy to share what surprised them, both the good and the hard parts.
- If you are planning a pregnancy, or have concerns about fertility, talk to a doctor. They can advise on health checks and preparation that fit your situation.
Friendship shapes our lives in more ways than we notice, from the music we like to the moments we choose to grow our families. Knowing that can help us make those choices a little more consciously, and enjoy sharing them with the people who matter most.
Sources: ScienceDaily (American Sociological Association release): Having children is contagious among high school friends during early adulthood; Balbo, N. and Barban, N., "Does Fertility Behavior Spread among Friends?", American Sociological Review, 2014.
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