But don’t expect to ever hear it promoted by anyone who will lose money because of it:
During the pontificate of John Paul II, there was also the breakthrough in scientific research that Paul VI had wished for in “Humanae Vitae”: the discovery of a method of birth control based on the monthly period of infertility, easy to apply and reliable. But the news of this breakthrough did not extend beyond Catholic circles in the developed world, and even there it was not sufficiently promoted in Western countries like Italy, while it had much more success in the Third World.
In Western countries, in fact, natural methods have continued to be considered not only completely ineffective, but also inconvenient and difficult to apply. And there is another characteristic, which is never mentioned, that has contributed to giving them a bad name: the fact that they are free. No pharmaceutical company had any interest in financing research on this form of birth control. Instead, it was to their advantage to heap ridicule on it and discredit it.
Things to consider before bashing Humanae Vitae. Plus much more to consider, in the whole article from which this is taken. It’s called “Cardinal Martini’s Jesus Would Never Have Written ‘Humanae Vitae’.“