I see these passages as instrumental in dispelling the myth that myself and no doubt many others have had growing up, that 'sex' was the original sin. " ...And they shall be one flesh." indicates to me that sex was happening between 'the man and his wife' at some point before the original sin occured and that this was no problem for God.
Not only was this NOT a problem for God but Genesis indicates that this is something that God expected to happen, "Therefore shall a man leave his mother and father...". You can't be a mother and father without children and you can't have children without sex; at least back then and excluding the divine birth (controversies not withstanding).