^ i think its 2 do with predicting when ure most fertile i.e. a week b4 ure period as that is when u ovulate, so that chancs of getting pregnant at that point in time is highest, so avoid intercourse during that period of time
Re: natural birth control
Abstinence is the sure and natural way of avoiding pregnancy.
Withdrawal, rhythm method are not.
STD' are not necessarily prevented by peeing.
And peeing to prevent pregnancy...lol