Advanced Maternal Age

What exactly is "advanced maternal age?" I don't consider myself much of an advanced age. Isn't 40 supposed to be the new 30? Who in the Hell came up with this term "advanced maternal age?" Today I went on FF to see the new posts in the IUI, IVF or Medical Assitance forum and someone decided to ask other AMAs about their history. It was so nice to see that this struggle is affecting so many other women. I think it's programmed in our society to wait to have kids until we are married, financially stable and have everything else first. Why is children last on our lists? We see people like Geena Davis, Jennifer Lopez and Madonna all having children later in life and we think we can do it too. Clearly, if you ask my fellow FFers, this is not always the case. Obviously, R's azoospermia would force us to pursue IVF anyway, but had we done this 5 years ago I might've been able to cough up more eggs and I would be pregnant by now. I realize I can't know what would've happened had I done things differently. But what I'm saying is that I wish I hadn't been so arrogant as to think I could have children whenever I wanted. And I wish someone would have told me this. Instead, people always said, "Oh...you have PLENTY of time." No, I don't.