Mother and son in New Mexico face jail time for incestuous relationship

[FatAndFaithless]

There are plenty of non-related couples who have high risks of certain birth defects as well, just by the nature of their genes and how they match up.  We don't make laws against them having kids.

The risk of genetic defects multiplies massively when both partners have similar genetic profiles. Guess when that happens? Yes, when both sexual partners are closely related, even more so when the relation is in the first degree (parent and child or brother and sister). The fact of the matter is that incest does make it far more likely that children of such a union will have genetic defects that will either make their lives harder or kill them than would normally be the case for children of unrelated persons (unrelated to a reasonable degree, you're not going to get two people who don't share a common ancestor somewhere).

Who arbitrates what degree is 'acceptable' for risks of genetic defects?  We don't make laws against two people breeding just because they're at risk of defects.  We don't even make laws prohibiting two people who have the same genetic defect, and might be certain to have a child with the same defect, from having children.

You can find it irresponsible, distasteful, or immoral, but there's no reason it should be illegal.

Hypothetical situation - a brother and sister are in an incestuous relationship. They get pregnant - the fetus is tested and found to almost certainly have a defect. The couple abort the fetus, then try again a year later. Should any of that be illegal?

Consider the same above situation, but instead of a brother and sister, it's two unrelated people whose genetic profiles line up in such a way that they are at extremely high risk of genetic defects as well, and they take the same course of actions as the brother and sister above. Should any of that be illegal?