July 25th is the 40th anniversary of Humanae Vitae, the papal document which reaffirmed the Church's teaching against contraception. 40 years ago Humanae Vitae "prophesied" that marriages and society would suffer if contraception became widely used. This has proven to be the case without doubt.
Professor Janet Smith wrote a wonderful article called Humanae Vitae: A Generation Later that is well worth looking into. She also wrote has another piece on the prophetic nature of the encyclical.
Here are some ideas for priests who want to preach on this topic from Human Life International: PREACHING HUMANAE VITAE. If you would like to read more check out Mary Eberstadt’s excellent article:"The Vindication of Humanae Vitae.”