Wow. I would lose it if my doctor said this to me. This is personal and no one's business. The doctor's business is your health, and that's it.
I know why you said what you did- you just wanted to shut her up. But really, you should not have had to rehearse a speech. You should not overthink this and provide people like this with a list of reasons / explanations. That gives some people the impression that the subject is up for a debate / negotiation. It's not. A flat out answer of "No, we are not planning to have children." is all you need. If pressed, repeat the same line again. It's not rude. Any further commentary from her would result in my reporting her and finding a new doctor- which maybe you should consider.
