Exactly this. That's why I find it hard to believe all the anecdata on here of all these women having their first baby at 43-44+.
The average is, in fact, 30-31 years old.
Birth characteristics in England and Wales - Office for National Statistics (ons.gov.uk)
And it's got fuck all to do with class or socio economic bullshit la la la. I know/have known women who are vicars, consultants, opticians, dentists, teachers, nurses, GPs, paediatricians, factory workers, checkout operators, bankers, sculptors, hairdressers, architects, graphic designers, musicians, artists, car mechanics, receptionists, admin assistants, nannies, childminders, engineers, florists, electricians etc etc. From working class to middle class to upper class. Dozens and dozens of women. Apart from 2, they ALL had their first baby by 37 years old.. The other 2 were 38 and 39... (The vast majority had their first baby by 33-34.)
Maybe some women DO have their first baby at 43-45 or older. I have just never met one. (And I live in a very middle class 'naice' area too. Full of very expensive properties. Some upper class folk here too.) Still, every woman I know in my village (of 700 people) had their first baby by their mid 30s. From the checkout operator to the admin assistant, to the farmer's wife, to the architect, and the sculptor. No first time mummies at 43+. Not one.