That's my theory. Here's why.
In college, one of my friends dated a girl who had cancer. Several months in, I asked him how the relationship was going. He stated bluntly, "Well, it's tough. Because I don't really want to get attached if she's going to go and die on me."
Yes, he's a horrible person (in general, not just based on that lone event). But that was a real fear based on real evidence. Understanding the reality of the relationship before entering into it caused him to enter with much more caution.
We're currently at the stage where you can have yourself completely genetically tested for less than $10,000. For that price, you can know your precise likelihood of carrying and falling prey to the full spectrum of disease. And that information will change your market value.
"Sure, Jane's not as hot as Donna... but with an 80% less chance of cystic fibrosis, it might be worth it?"