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The Effectiveness Of Natural Family Planning

John Kippley

Part 1 — INTRODUCTION TO EFFECTIVENESS

Part 1: Introduction: The Effectiveness of NFP
Part 2: Method Effectiveness
Part 3: User Effectiveness
Part 4: The Ethics of FDA and ACOG Regarding NFP
Part 5: References

There is no doubt about it: some physicians are well informed about Natural Family Planning and they strongly encourage its use. Some are so convinced about the medical and moral hazards of unnatural forms of birth control that Natural Family Planning (NFP) is the only form of conception control they will offer to their patients.

However, the fact that some methods of NFP can be 99% effective in the avoidance of pregnancy seems unknown to most of the general public--including many health care professionals. The fact that the fertility awareness which is a key element of modern NFP is also very helpful to couples of marginal fertility in seeking pregnancy is also unknown. Ignorance breeds prejudice, and this is just as true regarding NFP as it is about other areas of life; it applies across the board from the "man in the street" to the editors of health journals and women's magazines.

There are three basic reasons for widespread ignorance and prejudice regarding natural family planning.

First of all, many health care professionals are uninformed about the modern methods of natural family planning. Therefore, they group various natural methods that are entirely different together under the title of "rhythm". On the contrary, it is absolutely necessary to distinguish between different systems of natural family planning, just as it is necessary to distinguish between different unnatural methods such as the Pill and a postcoital douche. For example, what health care provider would average the best case for the Pill and the worst case for the douche and state the result as the effectiveness of artificial or unnatural methods of birth control? It is no less absurd to apply that procedure to various natural systems of family planning.

Secondly, many people including health care providers, are skeptical of anything natural. Their orientation is so much towards drugs, surgery and devices that they find it difficult to believe that common ordinary married couples can understand their mutual fertility well enough to achieve the same effectiveness associated with powerful drugs.

Thirdly, some organizations that specialize in or are oriented towards unnatural forms of birth control have been unfair in their treatment of NFP. Old rhythm studies from Latin America with low effectiveness rates are quoted and requoted, but a recent and well designed study by the U.S. Federal Government showing a 100% method effectiveness is ignored or misquoted.

One purpose of this pamphlet is to review the very solid basis for the statement that the Sympto-Thermal Method of Natural Family Planning can be used at the 99% level of effectiveness in avoiding pregnancy, using the same statistical criteria used for unnatural methods. This review makes that claim only for methods which include the temperature sign, and it does not make the claim for mucus-only systems sometimes known as the Billings Ovulation Method or the Hilgers (Creighton) Ovulation Method.

The second purpose of this pamphlet is to demonstrate the unfairness used by some groups in their treatment of NFP and to call for fairness.

The Sympto-Thermal Method taught by the Couple to Couple League and most other teaching organizations uses the two natural signs of cervical mucus and the waking temperature plus certain information from the woman's own previous cycle history, and these three factors are used together in a cross-checking way. Users are generally taught about physical changes in the cervix for further corroboration, but such observations are usually not included in the rules.

A short word on terminology:

Phase I: pre-ovulation infertility starting with the first day of menstruation.
Phase II: the fertile time
Phase III: postovulation infertility

The term "Pearl rate" refers to a formula developed in the 1930s by Raymond Pearl to measure the relative effectiveness of various forms of birth control.

Part 2 — METHOD EFFECTIVENESS

The Los Angeles Study
100% Method Effectiveness

Between 1976 and 1978, the U.S. Department of Health, Education, and Welfare conducted a prospective study to determine the relative user effectiveness of two different systems of Natural Family Planning.1 Participants were randomly assigned to either the Sympto-Thermal Method (STM) or Ovulation Method (OM) sides of the study. However, they were first screened to eliminate any couples who had a serious health, economic, or social reason to avoid pregnancy. The resulting group of 1257 couples had an average age of 28 and had only one child per family.

In the STM side of the Los Angeles study, couples determined the end of Phase I by using a calculation based on the woman's previous cycle history (short cycle minus 21 equals the last day of Phase I) and cross-checked that with the continued absence of mucus. They determined the start of Phase III by cross-checking three days of well elevated temperatures with four days of the disappearance of the cervical mucus which characterizes the fertile time.

The couples who followed these simple rules achieved a 100% effectiveness rate in avoiding pregnancy, i.e., zero unplanned pregnancies. (The couples who used the OM rules had 5.67 unplanned pregnancies per 100 woman years of exposure, i.e., about a 94% method effectiveness rate. Better OM results were achieved in a five nation World Health Organization study: a standard Pearl rate of 2.6; i.e. a 97.4% effectiveness rate.)2

A 100% effectiveness rate cannot be sustained in a large population and thus claims made for the STM state "99% method effectiveness."

The Fairfield Study
99% Method Effectiveness

Between 1970 and 1972, 1022 couples participated in a five nation (Canada, Colombia, France, Mauritius, U.S.A.) study called the Fairfield Study after the university of the principal investigator.3 The calculation used to determine the end of Phase I (short cycle minus 19 or 20) was more liberal than that used in the later Los Angeles Study; a three day temperature-only rule was used to determine the start of Phase III without cross-checking for the disappearance of cervical mucus. The couples who followed these more liberal rules achieved a method effectiveness rate of 99% according to the Pearl formula (9 unplanned pregnancies in 14,416 months of exposure).

The Roetzer Studies
99% and 100% Method Effectiveness

Dr. Roetzer has distinguished between the method effectiveness of Phase I and Phase II according to his rules.4 In his 1978 study, he reported that coitus during the first six days of the fertility/menstrual cycle yielded one pregnancy in 8,532 cycles, a Pearl rate of less than 0.2 per 100 woman years of exposure, i.e., well within a 99% effectiveness. Using a combination of three days of well elevated temperatures cross-checked by three days of the disappearance of more fertile mucus to determine the start of Phase III, couples experienced zero unplanned pregnancies in 17,000 cycles, i.e. a 100% method effectiveness rate.

The Doring Temperature-Only Study
99% and 100% Method Effectiveness

Dr. Gerhardt K. Doring tested the only pure temperature-only system reported in the literature--using a temperature based calculation for determining the end of Phase I as well as the start of Phase III.5 With the formula "earliest day (in previous cycles) of thermal shift minus 7 yields the last day of Phase I," there were 13 unplanned pregnancies among 37,035 cycles, a Pearl rate of 0.42 per 100 woman years, well within the 99% level of effectiveness. Among 307 couples using a three day very strong thermal shift pattern for the start of Phase III and confining intercourse only to Phase III, there were zero unplanned pregnancies in 11,352 cycles, another 100% method effectiveness rate with a limited population.

The Vincent Study
99% Method Effectiveness

Similar results were achieved in a French study published in 1967.6 Couples in this study had intercourse only in Phase III as determined by a rule similar to that of Dr. Doring., There was one unplanned pregnancy in 17,500 cycles yielding a Pearl rate of 0.07 per 100 woman years of exposure, well within the 99% level of effectiveness.

Conclusion 1. Studies conducted in Canada, Colombia, France, Germany, Mauritius and the United States have demonstrated a 99% method effectiveness for the Sympto-Thermal and Temperature-Only Methods. These studies were conducted under a variety of conditions and demonstrate beyond any reasonable question of a doubt that this extremely high effectiveness can be achieved by ordinary couples who receive adequate instruction and follow the relatively simple rules of these methods.

Part 3 — USER EFFECTIVENESS

In any group of people participating in any test of a method of birth control, there will be some couples who do not follow the rules. For simplicity, we will call them "chance-takers."

The term "user effectiveness" includes the pregnancies of couples who did not follow the rules — the "chance-takers."

The percentage of chance-takers will vary according to their relative motivation to avoid pregnancy and also according to the perceived difficulty of the method. Therefore birth statisticians have classified users into two categories: "limiters" and "spacers."

Limiters are those who desire no more children: for example, a couple in their mid-forties with five living children might classify themselves as limiters.

Spacers are those who consciously intend to have future children but want to delay pregnancy. Even within such a group there may be significant differences in motivation from that of delaying pregnancy a few months so birth will occur in a certain season to delaying pregnancy until an unemployed breadwinner is re-employed, etc.

Where significant differences in effectiveness rates are found between groups using essentially the same method, the differences say more about the makeup of the different groups or their training than it does about the method; where the members of two groups which are essentially the same have significant differences in effectiveness rates, the differences say something about the different methods.

The Los Angeles study was developed specifically to test for user effectiveness differences between the STM and the OM.7 Therefore the participants were randomly assigned to either side of the study, and the resulting populations were statistically very well matched.

The study population was essentially a group of spacers for two reasons: 1) no one with a serious reason to avoid pregnancy was allowed in the study; participants were warned that there might be an unplanned pregnancy rate of 25%, and they had to be willing to accept that risk to enter the study. In such a group of "spacers" it is hardly surprising that a number of couples decided to "take chances," i.e. have intercourse at a time indicated as fertile by the particular method. Thus, the STM group experienced a "user effectiveness" rate of 15 pregnancies per 100 woman years (i.e. an 85% effectiveness rate) while the OM group experienced a "user effectiveness" rate of 37 per 100 woman years (i.e. a 63% effectiveness rate). The designers of the study concluded that the difference was statistically very significant in favor of the Sympto-Thermal Method. (Significantly higher user-effectiveness rates were reported in the five nation WHO study of the OM:8 20.6 per 100 woman years according to the standard Pearl formula.)

The Fairfield study showed somewhat similar results.9 In the same study that showed a pure method surprise pregnancy Pearl rate of only 0.75, there was an overall user effectiveness rate of 5.49, still a most respectable 94.5% effectiveness rate. However when the spacers were analyzed as a separate group, the five nation average Pearl rate was 14.83 per 100 woman years — i.e., an 85% effectiveness rate.

The Austrian and German studies show a very narrow spread between method effectiveness, and that probably says that as a whole the couples in those studies were more committed to keeping the rules.

In the Roetzer study, the overall user-effectiveness Pearl rate of 0.8 (12 pregnancies in 17,026 cycles), is still within the 99% level of effectiveness.10

In the Doring study, there were 125 pregnancies in approximately 48,387 cycles, yielding a Pearl rate of 3.1 per 100 woman years, i.e. a 97% effectiveness rate.11

Conclusion 2. Studies conducted in Austria, Canada, Colombia, France, Germany, Mauritius and the United States have demonstrated a user effectiveness ranging from 85% to 99%. The evidence also strongly supports the common sense notion that the lower effectiveness rates will be found in groups which contain a significant proportion of couples who have no serious reason for postponing pregnancy.

For purposes of comparison, it should be noted that the 85% user effectiveness rate of the STM when used by spacers is equal to or higher than the user effectiveness of any other non-permanent method of birth control except the Pill.12

Part 4 —The Ethics of FDA and ACOG Regarding NFP

Part 1: Introduction: The Effectiveness of NFP
Part 2: Method Effectiveness
Part 3: User Effectiveness
Part 4: The Ethics of FDA and ACOG Regarding NFP
Part 5: References

In the light of this demonstrated effectiveness, the ethical propriety of certain allegations about natural family planning must be questioned. For example, the FDA Consumer for May, 1985 ran an article that listed "Natural Family Planning or Rhythm" as having an estimated effectiveness of "very variable, perhaps 53-86%.13 Correspondence with the editors and U.S. Department of Health and Human Services medical advisors to the FDA Consumer revealed that the basis for that very low figure were two Latin American studies. One was almost entirely a calendar rhythm study in Colombia. 14 and the other was a comparison between the Ovulation Method (OM) and the Sympto-Thermal Method (STM) also done in Colombia by some of the same people involved in a somewhat similar study in Los Angeles. 15

The Colombian calendar rhythm study was conducted in six birth control centers and had many problems. The overall Pearl rate was 47.0 pregnancies per 100 woman years which translates to a 53% effectiveness rate.

The rhythm investigators also studied the effectiveness of the Pill in those same Colombian birth control center and reported a Pearl unplanned pregnancy rate of 10.5 or an 89.5% effectiveness rate.

Thus, the FDA authorities used a study that reported a 89.5% effectiveness rate for the Pill and a 53% effectiveness rate for calendar rhythm. However, they ignored the Colombian 89.5% figure for the Pill and reported only a 99% figure, supposedly from other sources. In fact, they did not even report an 89.5 to 99% range in effectiveness for the Pill; they reported on the single highest figure. Can that be called ethical and fair?

The Colombian OM-STM comparison study used by the FDA to allege low effectiveness for NFP failed to report on "method failures," concentrating entirely on user effectiveness. With the life-table method of statistics there was a net pregnancy rate of 24.2% for OM users and 19.8% for STM users. In terms of the older Pearl formula, the pregnancy rates were 33.8 per 100 woman years for OM users and 26.0 for STM users during the one year of the follow-up phase.

As the authors reported, "The results of this study indicate that these two methods of NFP cannot be considered as simple methods of family planning but as a new way of life which requires changes in sexual behavior cannot be achieved in a short period of time.. The degree of motivation toward following periodic abstinence is related to cultural factors that make abstinence difficult to practice in Colombia."

Precisely. This was also demonstrated in the previously cited five-nation STM study in which the results from Colombia were so markedly different from the North American, European, and Asian figures that they were treated separately. 16 However, when the rates of 94.5% overall use effectiveness and 85% spacer use effectiveness are cited from that study, such figures include the Colombian results (and would be higher if they did not).

Thus it is well known among birth control professionals that if you want to quote very low effectiveness rates for any form of NFP, you go to Colombia. However, is it ethical to write for a North American audience and quote only the Colombian studies and ignore the North American and European studies which are far more relevant?

It should also be noted that the 86% figured quoted as the high end of the range for NFP is actually almost the low end of the range in the only federally funded American STM study. 17 As mentioned previously, the authors found a 100% method effectiveness rate and an 85% user effectiveness rate for the Sympto Thermal Method.

In the introduction to the FDA article, the author noted that the range of effectiveness could vary as couples either followed or did not follow the rules. It is no excuse to say the FDA wanted to report only the figures for groups containing chance-takers; if that were the case, a range would have been reported for the Pill.

To recapitulate, in an article purporting to compare birth control options in a publication designed for the American consumer, the FDA:

  1. Withheld a relatively low effectiveness figure for the Pill, a figure reported in study used by the FDA.

  2. Withheld the STM 99% effectiveness figures available to anyone writing in the field of birth control. The difference in treatment is unethical and unfair.

  3. Distinguished between different unnatural methods of birth control.

  4. Mixed up and confused the different methods of natural family planning. The difference in treatment is unfair and unprofessional.

  5. Failed to report any sort of range of user effectiveness for the Pill.

  6. Reported only the highest possible figure for the Pill.

  7. Reported what may be the lowest figure ever reported for calendar rhythm.

  8. That's unethical and the difference in treatment is unfair.

Such a combination of unfairness, unethical reporting, and unprofessional writing is simply intolerable among those employed as our "public servants."

* * *

Another unethical treatment of NFP is the work of the American College of Obstetricians and Gynecologists (ACOG). This organization has unfortunately adopted a pro-abortion stance, and thus its orientation towards contraceptive, abortifacient, and surgical methods of birth control is understandable. Nevertheless, if an organization is going to treat of NFP at all, it has an ethical responsibility to treat it fairly and accurately.

In 1985 ACOG produced a slide-rule form of birth control effectiveness comparison which listed Natural Family Planning as producing 24 unplanned pregnancies for every 100 couples who used it. 18 Their "Natural Family Planning" figure is identified as meaning "periodic abstinence, symptothermal, temperature, mucus."

Correspondence with ACOG revealed two sources used for their "NFP" numbers. The first was an article in a Planned Parenthood publication. 19 The authors attempted a generalized approach to all methods of birth control employing information from two retrospective surveys in 1973 and 1976. Their figure for the Pill was a 2.4% failure rate in the first year; their figure for "rhythm" was 23.7. "Rhythm" was unspecified, and in 1973 and 1976 retrospective surveys, the term in all probability includes every imaginable sort of makeshift "wrong way" rhythm.

The second source was the 1984-1985 edition of Robert A. Hatcher's Contraceptive Technology. 20 Table 10:2, "Efficacy rates: fertility awareness of birth control" lists figures for ten different systems of NFP from calendar-only to temperature-only, mucus-only, and sympto-thermal, and the effectiveness rates ranged from 70% (calendar-only) to 99.7% (Phase III only, temperature-only). The 1985 ACOG birth control calculator apparently settled for the Schirm-Planned Parenthood figure of 24 (above) which is also quoted by Hatcher. 21

This is unethical and unprofessional. The "24" figure is derived from two retrospective studies about a completely unspecified and catch-all "rhythm," and it is a serious misrepresentation to state that it represents "periodic abstinence, sympto-thermal, temperature, mucus." Proponents of natural family planning would be ridiculed if they relied upon a 1968 Colombian study to state that the Pill had an unplanned pregnancy rate of 10.5% or if they averaged all the unnatural methods listed by Hatcher and said that unnatural methods had an average unplanned pregnancy rate of 11.4%--true but quite irrelevant. The same standards need to be applied to the so-called professionals in ACOG and the FDA.

Fairness Needed

The FDA and ACOG treatments of Natural Family Planning are misleading and unfair. It is not only unethical for knowledgeable people to mislead the general public, but it is unfair both to the general public and to the many thousands of ordinary couples who are successfully using modern methods of natural family planning and who deserve knowledgeable support, not ridicule, from their physicians.

Fairness dictates that ACOG and all branches of HHS inform the public about method and user effectiveness rates that have been reported in European and North American studies. No matter how effective NFP is, there will be many who will not choose it simply because they will not accept even the idea of periodic abstinence; but such people at least deserve to know the real facts about NFP if for no other reason than that they can then deal more honestly with their own reasons for choosing one method or another.

With regard to the FDA, a division of the U.S. Department of Health and Human Services, it should be noted that another branch of HHS, the Bureau of Community Health Services, published a brochure, "Natural Family Planning" in which it listed the Sympto-Thermal Method as having a "Method Effectiveness" of 98% and a "User Failure Rate of 10-15" pregnancies per 100 woman years. 22

That's not entirely accurate since the demonstrated method effectiveness is 99% and user-effectiveness has been demonstrated to range from 1 to 15 pregnancies per 100 woman years in European and North American populations, but it represents a much fairer treatment than that given by the FDA.

Fairness also dictates that ACOG and all branches of HHS distinguish between the various forms of natural family planning. The above mentioned HHS brochure on NFP distinguished four different systems: Temperature-Only, Mucus-Only, Sympto-Thermal, and Calendar Rhythm. The HEW (now HHS) Los Angeles study reported statistically significant differences in the use of the Ovulation Method and the Sympto-Thermal Method, and interested health care providers and prospective user couples deserve to know these facts. 23

Fairness requires that the range of STM user effectiveness be attributed primarily to choices of the user couples, themselves, not some trick or fault in the method.

For Birth Control Comparisons

The birth control comparison charts and graphs that appear in popular magazines devote much space to the Pill: more space needs to be given to the different methods of natural family planning.

In the style of such birth control comparison charts, the following would be a fair treatment of the Sympto-Thermal Method:

Effectiveness

Effectiveness depends on how correctly the ST Method is used. Of 100 couples using the STM correctly for one year, one or less will become pregnant. Of 100 couples using the STM but with some not following the rules, anywhere from 3 to 15 will become pregnant depending upon the frequency of "taking chances", i.e., intercourse during the fertile time.

Advantages

All natural; no drugs or devices are needed. Inexpensive. No continuing cost after initial training, thermometer and charts. Acceptable to all religions. A scientific method based on systematic observation and recording of the signs of fertility and infertility.

Disadvantages

Requires systematic charting. Requires mutual decisions about abstinence.

Side Effects

No physical effects. Most couples report improved marriages and sex lives. Some couples do not accept periodic abstinence.

Health Factors to Consider

No health risks. Increased body-awareness can lead to early detection of physical disorders. Increased fertility awareness can help couples of marginal fertility to conceive.

Proponents of natural family planning can find much more to say about the advantages of NFP, but the above was written in the style of a birth control comparison chart published some years ago by the FDA and adopted or adapted by many popular magazines in recent years.

The time has come for ACOG, the government and the media to be fair in their treatment of natural family planning. It is not a panacea for anything, but the STM is a highly effective, healthy and inexpensive form of family planning that enables most married user-couples to state they enjoy improved sex lives and better marriages. It's a story that deserves both attention and fair treatment.

Part 5 — REFERENCES

1. Maclyn E. Wade, Phyllis McCarthy, et al., "A Randomized Prospective Study of the Use-Effectiveness of Two Methods of Natural Family Planning," Am J. Ob. and Gyn. 141:4(Oct 15, 1981) 368-376.

2. World Health Organization, "A Prospective Multicentre Trial of the Ovulation Method of Natural Family Planning. II. The Effectiveness Phase," Fertility and Sterility 36:5 (November, 1981) 591-598.

3. Frank J. Rice and Claude A. Lanctot, "Results of a Recent Study of the Sympto-Thermal Method of Natural Family Planning," Linacre Quarterly 45:4 (November, 1978), 388-391.

4. Josef Roetzer, "The Sympto-Thermal Method: Ten Years of Change," Linacre Quarterly 45:4 (November, 1978) 370.

5. G.K. Döring, "The Reliability of Temperature Records as a Method of Contraception," (Über die Zuverlassigkeit der Temperaturmethode Zur Empfangnisverhutung) Deutsche medizinische Wochenschrift 92:23 (June 9, 1967), 1055-1061. Abstracted in 1968 Yearbook of Obstetrics and Gynecology, p. 354.

6. B. Vincent et al., Methode Thermique a et Contraception: Approaches medicale et psychosociologique (Paris: Masson, 1967) 52-73.

7. Wade, op. cit.

8. W.H.O., op. cit.

9. Rice, op. cit.

10. Roetzer, op. cit.

11. Döring, op. cit.

12. Frederick S. Jaffe, "Commentary: Some Policy and Program Implications of 'Contraceptive Failure in the United States,'" Family Planning Perspectives 5:3 (Summer, 1983) 133-142. Delayers (spacers) are reported to have these pregnancy rates with the various methods: Pill, 7%; IUD, 15%; condoms, 21%; diaphragms, 25%; foam, 36%; douche, 47%.

13. Judith Willis, "Comparing Contraceptives," FDA Consumer 19:4 (May, 1985) 28-35.

14. Mario Jaramillo-Gomez and Juan B. Londono, "Rhythm: A Hazardous Contraceptive Method," Demography 5:1 (1968) 433-438.

15. Jorge E. Medina, M.D., "Comparative evaluation of two methods of natural family planning in Colombia," Am J. Ob. and Gyn. 138:8 (Dec. 15, 1980) 1142-1147.

16. F.J. Rice, C.A. Lanctot and Consuelo Garcia-Devesa, "The Effectiveness of the Sympto-Thermal Method of Natural Family Planning. An International Study." (Mimeographed reprint of an address given June 23, 1977, at the scientific congress held in conjunction with the First General Assembly of the International Federation for Family Life Promotion in Cali, Colombia.) p. 8.

17. Wade, op. cit.

18. The American College of Obstetricians and Gynecologists, Benefits, Risks & Effectiveness of Contraception, 1985.

19. Allen L. Schirm and others, "Contraceptive Failure in the United States: The Impact of Social, Economic and Demographic Factors," Family Planning Perspectives 14:2 (March/April, 1982) 68-75.

20. Robert A. Hatcher and others, Contaceptive Technology 1984-1985, (New York: Irvington) 1984.

21. Ibid., Table 1:1.

22. Bureau of Community Health Services, Natural Family Planning, DHEW Publication No. (HSA) 79-5621.

23. Wade, op. cit.

 

 

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