This method was first used during the 1920's and is one of the most recommended method for those who have regular menstruations. It is done by following the strict rule of only having sex 14 days before menstruation, plus or minus 2 days.
The author of this website, Ronald Joseph de Leon, is an Organizational Communication Major in De La Salle University, Manila that supports the passage of the Reproductive Health Bill...
Though being a supporter doesn't mean he'd always be. :)