Midwives have been told about the benefits of “close relative marriage” in training documents that minimise the risks to couples’ children.
The documents claim “85 to 90 per cent of cousin couples do not have affected children” and warn staff that “close relative marriage is often stigmatised in England”, adding claims that “the associated genetic risks have been exaggerated”.
Usually the argument goes into the ethics of bearing children in a way that, knowingly, creates a significantly and markedly higher risk for every kind of disorder reducing the child’s QOL. I don’t usually find this argument anywhere near airtight, since there’s a plethora of other ways to do that that aren’t banned AND this veers into eugenics territory. But that’s the argument I’ve seen, at least.