Do any sects permit consensual open marriages?

1 Corinthians 7:4 says: > The wife does not have authority over her own body but yields it to her husband. In the same way, the husband does not have authority over his own body but yields it to his wife. If a man sleeps with another woman without his wife's knowledge or consent, that would be adultery. But what if he does so at the **behest** of his wife, with her knowledge and consent, even instigation, as Abraham did with Hagar at Sarah's suggestion? Is he then relinquishing "authority" over his own body but yielding it to his wife? I'm interested in an _overview_ of the views of various Christian denominations on this, or other forms of consensual (on the part of both/all parties) open marriages - are there any that consider them to be okay?