When should you get pregnant?

NewScientist advises:

IT’S a question many people will ask themselves at some point in their lives: when should I start a family? If you know how many children you’d like, and whether or not you would consider, or could afford, IVF, a computer model can suggest when to start trying for your first child.

Happy with just one? The model recommends you get started by age 32 to have a 90 per cent chance of realising your dream without IVF. A brood of three would mean starting by age 23 to have the same chance of success. Wait until 35 and the odds are 50:50 (see “When to get started”).

(Archived here.) I am surprised at this. It seems to imply that women have to spend 20 years trying to get pregnant just to have 3 kids.

Before birth control, women would sometimes have 10 kids.

Mark Zuckerberg's wife is probably over 30, and she is pregnant after 3 miscarriages. So it is apparently taking her several years (at least) to have 1 child.