I don't think that's rude at all. It's a simple question. If they're saying it rudely, that's different. But many twins and triplets ARE conceived via IVF. And many are concieved naturally. It's not rude, it's simple curiousity. Maybe that person is looking into IVF for themselves. Maybe they are worried about having twins because it runs in their own family. Maybe they are jerks who are just being jerks .... to each their own. There are certainly worse things you can ask, or insinuate.

Well I think they should mind their own business and I would tell them that!

well, I knew a woman who had quads (3 girls and 1 boy) and it's REALLY hard not to ask that question in that situation. and Yes, it was IVF.

I don't see how it WOULDN'T be rude to ask somebody how they're kids were conceived! You don't walk up to a stranger and ask about they're sex life! I get that some twins did need IVF, but not only does it make you look stupid, but WHY would you ask that? I used to Nanny my sister's twins and everyone thought I was the mother and asked ENDLESS questions, so I know how this woman feels! My brother and sister are almost 2 years apart, and people would still ask if they were twins! Me and my mom would look at them as it they we're crazy. ;-)