I don't have a wife or a biracial baby but.
geoffrya open my eyes to think about this and this is what I came up with.
If the baby is a planned birth by those involved then it is the husbands baby to raise with his wife.
If both the wife and husband agree to a marriage giving her sexual freedom and she ends up with an unplanned pregnancy , If the husband truly loves his wife they should except the baby as their own. Cuckolding is risky so I think because they are in it anyway, they should take the responsibility. The old saying goes if you play you pay.