Interesting that Catholics consider sex between a husband and wife as "carnal relations". Sex between a husband and wife is God's idea and there's nothing wrong with it at all.
Sex between husband and wife — or between anyone and anyone for that matter — is carnal relations as it involves their flesh (carnalis, “in the flesh”).
It is not sinful to engage in sex between a husband and a wife provided no contraception is used and the sex is not degrading to any side.