Well for this one I assume you really want to get pregnant and it doesn't happen by accident... I think you should wait until you at least have finished your education, your boyfriend / husband is able to care for you financially (or support you at least) and you are able to go back to your job if you want to after your pregnancy. So that would mean somewhere in your twenties I guess. I wouldn't advise earlier since it is really stressful to care for a child / be pregnant and at the same time get a proper education. And all your friends will go to parties and stuff and will probably not be able to relate to your situation, so that's difficult. To be honest I think if you are way older than twenty to thirty it's kind of weird as well... I mean if you imagine you get pregnant at 45 that means you're already over 60 when your child comes of age. If your child, too, waits 'til it's 40 to become a parent the chance isn't that high for you to become a grandmother, I mean you would already be 80 when your gandchild is born...