Well, yes, it IS all about understanding among couples. And you're failing to understand her. You're completely dismissing her desire to have a biological child, carried by her. You're failing to understand or care why it's important to her, and you're basically telling her she is defective, not good enough to carry a child.
And based on what? You obviously have no problem sharing her medical history with us, so I think it's glaringly obvious that no doctor was consulted to discuss possible medical consequences of your wife getting pregnant. You just come to the conclusion she shouldn't get pregnant all by yourself. So much for understanding between couples.
It's okay that you're concerned. It is NOT okay that you unilaterally decide that your wife shouldn't get pregnant, not if having kids at all isn't the issue. You should be telling her "let's see a doctor to make sure it's safe" instead of "I don't think it's safe, so you're not allowed."