When God made the first man and woman he made sure his First Couple understood about where babies come from.
'Adam,' He said, 'you'll need to leave the Missus to her own devices for five days every month.'
Adam readily agreed but was puzzled by God's edict.
'Lord,' he said, 'how will I know my wife is menstruating?'
'Good point, Adam,' God replied, 'and to help you out I will send you some very obvious, tell-tale signs just before the blood starts flowing. Call it PMT if you like.'
Relieved at the tip-off Adam then plucked up courage to implore God for more details about the sex ban during a woman's time of month.
'Well,' said God, 'there are all sorts of invisible karmic conditions to making love when a woman is on their period. I'll see what I can do to help you figure it out for yourself.'
And that's why ever since tampons have strings attached.