I have a theory, for those Christian women who marry non-Christian men, it would appear that their children, if be males, are more prone to sexual immorality than others. Such as the prominent case of Saint Augustine.
I cannot say the same for Christian males who marry non-Christian women, as I do not have sufficient data. But I'm sure there's some sort of common degeneration there.
As for marriages between different ethnic groups, I do believe that both parents would have to seriously hold tight to God. Otherwise, it may be likely that their children are prone to facing the judgment similar to that of Sodom and Gomorrah, even Noah's time.
Of course, all these, if God permits, could be offset by God's mercy before even one prays in sorrow and regret and repentance. As for each family, we are all under God's mercy, none of the above theories should encourage divorce or anything other than holy union in Christ, our Savior.