Natural Family Planning: Mucus-only Systems

Recently I saw a blog that raised my concerns about mucus-only systems.  First, some background.  The late Fr. Paul Marx OSB conducted an NFP symposium every summer in the Seventies.  I attended these from 1971 through 1978 and heard Dr. John Billings give his talk each year.  He was such a convincing speaker that he would leave me wondering why we taught the cross-checking Sympto-Thermal system.  That question evaporated when I realized that there was at that conference another meeting to which I was not invited.  The Ovulation Method (OM) teachers would get together to discuss real-life situations.  They were finding that in real life things were not as simple as in the talks by Dr. Billings.  The temperature sign can be a  tremendous help and especially when the mucus signs are ambiguous or difficult to interpret.  By the way, Fr. Paul Marx was a supporter of NFP International.

At the talks by Dr. Billings, I heard him say two things that are troubling to this day.  In one talk he explained why he and his associates had dropped the temperature sign.  He said it was too easy.  It was so easy to use and interpret the temperatures that their Sympto-Thermal Method (STM) users were getting sloppy with their mucus observations.  Thus, his method systematically deprives his mucus-only users of the very-easy-to-use temperature sign.  Our answer to this problem is to point out that each sign is very important, especially in some situations.  If a couple decides to use only one sign, that’s their business, but we strive to give them the freedom to choose.  I strongly object to the deliberate withholding of this information, the deliberate reduction of couples’ freedom to make informed choices.

I also heard Dr. Billings explain that his system does not teach the teachings of the Church regarding birth control.  He used the word “crutch” in saying that his method stands on its own merits as a method of birth control and does not need the “crutch” of religion.  The Hilgers system likewise advertises that it is open to people of all faiths.  He certainly doesn’t encourage any immoral behaviors, but his system does not explicitly teach Catholic teaching on unnatural forms of birth control.  A Hilgers user-couple once told us that such a lack of specific teaching led them to practice masturbation during the fertile time until they somehow got our materials.  In our manual’s witness chapter, one gentleman says he and his spouse used our 1996 manual for self-instruction but skipped the sections on morality and resorted to masturbation during the fertile time. They finally read those sections and repented.  I am sure that these cases are not at all exceptional.  In the mid-Seventies, a secular fertility-awareness book openly recommended oral sodomy although it condemned anal sodomy on grounds of being unsanitary.  I think it is imperative to state the specific unnatural forms of birth control.

Perhaps when the Billings dropped the teaching of morality, there were no immediate bad consequences because the users were made very much aware of the fullness of Catholic teaching by their Catholic education and parish priests.  Certainly that cannot be counted on today.

I am more convinced than ever that it is imperative to teach the covenant theology of the marriage act simply because it is so easy to grasp.  It also makes it very easy to understand the dishonesty of “marriage acts” outside of marriage.

Lastly, the Billings method of birth control is not as effective as it is sometimes claimed to be.  Right after Humanae Vitae, the U.S. bishops founded the Human Life Foundation to assist couples to live the teaching of the encyclical.  The Foundation persuaded the NIH to conduct an impartial study to determine the relative effectiveness of the STM and the OM.  It was published in 1981, stating that there were approximately twice as many surprise pregnancies in the OM group.  Drs. Billings and Hilgers criticized it at length even though they had been consultants to the study.  For example, they found fault with the study’s inclusion of unmarried couples.  Does anyone have good reason to think that unmarried couples are less motivated to avoid pregnancy than married couples? The bottom line is that the US Bishops through their Human Life Foundation sponsored a study which gave the above results, but many or most dioceses have ignored those results. In other words, while the OM may be very good, the comparative study showed that it is second best.

Couples have a right to know all the common signs of fertility, ecological breastfeeding, and the covenant theology of the marriage act.

For readers interested in what we teach at NFP International, go to and purchase Natural Family Planning: The Complete Approach.

John F. Kippley


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