Teens - Forget it.
Twenties - No. You should be partying, travelling and living the high life, preferably in London.
Early thirties (30-32) you should be building your career.
32-35 - probably acceptable. Many feel 32/33 on the young side.
35-38 - just tolerated. Many feel 37/38 is on the old side.
38+ no. You will die, have a child with disabilities and really how selfish. (If you can have one at all, that is.)
Disclaimer, I think the above is bollocks.
Have a baby when you want to have one.