No.
I think that every couple has to see their family as a ministry in itself and it sends the wrong message to unbelievers when a missionary serves with an unbelieving wife. (BTW this is assuming they were married before he was saved, I don't think missionaries should marry unbelievers either). The ministry is also a huge burden on the family and its unwise to put that stress on a woman who doesn't see it for the glory of Christ.
You can listen to Pastor John Piper talk about it also at:
