Rock solid science starts with rock solid scientists who have a strong desire to seek answers, reasons and explanations not just for their subject of interest but for many things that surround them. The scientists involved in the development of the Billings Ovulation Method® were Drs John and Evelyn Billings and Professors Emeritus James Brown and Erik Odeblad. What started as a collaboration between scientists became a life-long friendship.

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.

Fertility is a transient biological state that depends on the fertility potential of the couple. During a women’s lifetime, the ovary will go through different states of hormonal secretion and ovulation. The concept of the ovarian cycle as a continuum considers that all types of ovarian activity encountered during the reproductive life are normal responses to different environmental conditions in order to ensure the health of the mother and child.

In the 30 years fertile life of women, only a few days in each cycle are fertile and the rest of the time is infertile. People of insight have long considered making use of this natural phenomenon to regulate fertility. Early methods of natural family planning (rhythm, basal body temperature, symptothermal, etc.) are unsatisfactory for fertility regulation and the Chinese people did not accept them. In the early 60’s, Drs. J.J. and E.L. Billings and their colleagues discovered the interrelationship between the cervical mucus and the cyclic changes in the ovarian hormones and fertility and alleged the use of mucus symptom as the main index of ovulation and fertility applicable to all phases of female reproductive life. This is a milestone in the study of natural family planning.