It’s very hard to build a genuine community for a transient audience.
Communities for teenage entrepreneurs all suffer the same problem. By the time the audience is old enough to care and connect with others, they only have a few years of participation before they want to associate with older entrepreneurs.
Communities for account executives, interns, pregnancy, people getting married, and people facing a major surgery etc… forcibly limit the amount of time members will remain. In the process, you lose a lot of tacit knowledge.
It’s still possible to build a community for these audiences, but it’s better to focus on psychographics (what they think/feel about different issues), as opposed to demographics/habits. Don’t imply a short-term circumstance, target a belief/feeling that’s associated with that age.
Many young people entering a profession belief a fresh approach is needed, want to rise quickly in their fields, embrace new technology (and believe that technology should be embraced in their jobs).
If you can find a belief/feeling that’s associated with that short-term circumstance, you can build a community with a much longer retention rate.
Instead of building a community around pregnancy, you can build a community for mums that want to continue their careers. This includes the short-term pregnancy, but also encourages groups to form and share advice/support throughout the early years.
Looking for a belief and desire that your audience has, not just what the audience is and based your community concept around that.