This paper is a tribute to outstanding research about the Billings Ovulation Method®: it is a fact that Billings Ovulation Method® has been subjected to more scientific research of the highest standard than any other method of regulating fertility, natural or otherwise, and it is now essential knowledge for the medical profession.

The late respected director Anna Cappella was a tireless and passionate supporter of the Billings Ovulation Method®, as well as a friend and collaborator of Drs John and Evelyn Billings: the Centre on Natural Fertility Regulation (NFR) was born, from their partnership, at the Catholic University of the Sacred Heart in Rome, where couples have searched and found qualified professional advice on this Natural Method and a careful approach to the values of the person, respectful of the ethical issues related to the answers and reasons of the Magisterium with regard to sexuality and fertility.