I am loving this discussion.
There is another factor when women have children, especially in the entertainment world where women need to be seen as interesting, strong, exciting and sexy, but also in other not so glamorous backgrounds: having children suddenly turns women "boring". It's not very politically correct to say this, but there's this phenomenon in which a young, thin, sexy woman who is a famous singer/actress/entertainer has a massive following who admire her not only for the work she does, but for what she represents.
And then children arrive. And that vibrant, beautiful, carefree woman who talked about exciting things suddenly spends her days breastfeeding, and heating bottles of formula, and having sleepless nights, and starts sentences with "as a mother...", and becomes very judgmental about parenting techniques, and baby-feeding, and talks endlessly about nappies, and goes to after-school events.
Frankly, for the "public", the previous exciting and interesting woman may as well be dead. And I haven't even started on the "sexy" part of it that often goes down the toilet as soon as babies arrive.
It's what I call the "Katniss Everdeen effect". One of the most amazing, exciting, inspiring female heroes in literature (in my opinion, that is)... and then you get to the last bit of the last book (WARNING!!! MASSIVE SPOILERS) decides to have children with Peta, which is something she never considered before and I did not see coming... and suddenly she becomes a bit... just... meh. Then she is all about "these world I leave to my children", and "I love them so much" and "my children this, my children that". And you read that with massive disappointment, missing the brave, kick-ass Katniss of the three books, and just wish she had not ended up getting together with that boring Peta and having the boring, mundane, predictable life of a mum.
Because let's admit it, for most women their children are these amazing people who are the centre of their world and fill them with immense love and wonder every day. But for everyone else, her children are just utterly average kids you wouldn't look at twice on the street. Hearing a mum talking about her children for more than 5 minutes is often unfathomably dull.
Surprisingly, this tends not to happen with men, who even after having kids can still maintain the careless, sexy, adventurous, interesting persona. Often because someone else (a woman) is doing all the boring stuff with his kids, and because men tend not to be thinking about their children all the time.