Natural Family Planning

by John H. Geerling

American Family Physician
November 1, 1995
Copyright 1995 American Academy of Family Physicians
Vol. 52 ; No. 6 ; Pg. 1749; ISSN: 0002-838X

A better understanding of reproductive anatomy and physiology has led to newer methods of natural family planning, including the ovulation method and the symptothermal method. Studies have shown that 1 percent of couples who consistently and correctly use either of these methods conceives during one year of use. However, in the absence of standardized interpretation of study results, use-effectiveness data of these methods vary widely. The lactational amenorrhea method may be used in selected patients during the first six months postpartum, and its effectiveness in avoiding pregnancy is reported to be as high as 98 percent. Advocates of natural family planning promote these methods as inexpensive and safe ways to determine periods of peak fertility and point to the potential benefit of increased communication in a relationship.

While the various methods of natural family planning are readily learned, even by couples in developing countries, the methods most commonly promoted and taught in the United States require couples to attend several learning sessions with qualified instructors. This article will alert the family physician to important concepts in natural family planning and clarify misconceptions.

Female Reproductive Anatomy and Physiology

During the menstrual cycle, a surge of luteinizing hormone usually precedes ovulation, while a surge of estrogen usually precedes the surge of luteinizing hormone. The estrogen surge causes the columnar cells located in the endocervical crypts to produce a clear, stretchy, lubricative mucus (Figure 1), hereafter referred to as type E mucus. Human cervical mucus can best be described as a hydrogel consisting mostly of water and mucins, or glycoprotein polymers. In type E mucus, the mucins form linear structures, which in turn aggregate to form micelles. These micelles arrange themselves in parallel orientation to allow increased sperm penetration.

The water content of type E mucus is generally 92 to 95 percent, but this proportion increases to 98 percent around the time that ovulation occurs. Increased water content gives the mucus its increased elasticity, or spinnbarkeit. The concentration of sodium and potassium salts in the mucus also increases as ovulation approaches. As a result, periovulatory mucus forms a fern pattern when dried on a microscope slide Figure 2).

After ovulation has occurred, progesterone is the dominant hormone. Progesterone abruptly halts the production of type E mucus and stimulates the crypts to produce a sticky opaque mucus, referred to here as type G mucus. Type G mucus has a decreased water content and an increased mucin content. After ovulation, the mucin is arranged as a dense network; micelles do not form and there is extensive cross-linking (Figure 2). Sperm penetration is nearly impossible when this type of mucus is present. Because progesterone is thermogenic, it causes an increase in the basal body temperature, generally in the range of 0.4 degree F to 1.0 degree F.

An unfertilized egg can live for 12 to 24 hours. The presence of type E mucus allows the sperm to survive three to five days in the cervix. In the absence of type E mucus, sperm die within hours in the vaginal environment. Also, morphologically defective sperm are filtered out by type E mucus, which prepares the remaining high-quality sperm for successful fertilization. [1]

The concept of natural family planning is based on the fact that ovulation typically does not occur more than once during the same menstrual cycle, unless it is within the same 24-hour period. 2 An equally important consideration is that while intercourse may hasten by a few hours the rupture of an already ripe follicle, intercourse-induced ovulation, which occurs in certain mammals, does not occur in human beings. [2]

The length of the preovulatory, or follicular, phase of the menstrual cycle varies considerably and is responsible for variations in cycle length. The average length of the postovulatory or luteal phase is 13.7 days. 3 While the normal range of the luteal phase is nine to 17 days, the length of this phase within a given woman is usually consistent. [3]

One study involving 25,825 women-years of menstrual experience established that the average length of the menstrual cycle is 30.1 days at age 20 and that the average length of the cycle steadily declines with age (Table 1). [4] Furthermore, a study of 30,655 menstrual cycles in 2,316 women found that no more than 16 percent of cycles were 28 days in length in any age group.[5] Thus, obstetric and gynecologic evaluations and treatments based on the "standard" 28-day cycle with presumed ovulation on the 14th day should be reconsidered.

TABLE 1: Length of Menstrual Cycle by Age Group
Derived from Treloar, et al. 4

Age
(years) 		Average length
of cycle (days) 		Range
(days)
  20   30.1 23.6 to 36.6
  25   29.8 24.0 to 35.6
  30   29.2 24.2 to 34.2
  35   28.2 23.7 to 32.0
  40   27.4 22.9 to 31.9
 
(This table is in a table format which requires a browser which supports HTML 3 or higher.)

Calendar Rhythm Method

The relationship between ovulation and the start of the next menstrual period was first established around 1930. This information was used to develop calendar calculations which, when based on a certain number of previous cycles, would help a couple determine when a woman could be considered infertile during future cycles.

While the calendar rhythm method was used for several decades, it has not been promoted as a method of natural family planning for many years. While women who have regular menstrual cycles are able to use the calendar rhythm method successfully, women with irregular cycles, women who are breast feeding or women with postponed ovulation cannot depend on the calendar rhythm method. Because at least 25 percent of women who present to a natural family planning teaching center will be classified in one of these categories, [6],[7] alternative strategies to predict ovulation are necessary.

Ovulation Method

Since the middle 1800s, it has been understood that conception is most probable when the cervical mucus is m its most fluid condition. But this information was not incorporated into methods of natural family planning until John Billings, an Australian neurologist, began his research in 1953. In 1964 his wife, Lyn Billings, a pediatrician, established that women of all reproductive categories can make accurate mucus determinations. In 1964, the ovulation method of predicting fertility was described and in 1972, the ovulation method was introduced in the United States. Also in 1972, the first prospective trial of the ovulation method was published. [8] A number of published studies have been performed in many different countries since the 1970s. [7],[9-13]

The ovulation method relies solely on characteristics of the cervical mucus to accurately define the period of fertility and does not incorporate internal examinations. The peak mucus sign is considered to be the last day that cervical mucus is clear, stretches easily or has a lubricative quality. The characteristics of cervical mucus during this time have been likened to the qualities of raw egg white.

Several studies have demonstrated that the existence of clear, easily stretched or lubricative cervical mucus, as determined by external self-examination, is closely correlated with the estimated time of ovulation determined by hormonal assay studies. [3],[14],[15] The largest of these studies 3 evaluated 65 menstrual cycles in 24 women and reported excellent correlation between the peak mucus sign and the estimated time of ovulation (Table 2).

TABLE 2: Relationship of the
Estimated Time of Ovulation
and the Peak Mucus Sign

Occurrence of estimated time of ovulation Cumulative number
(N = 65)		 Cumulative
percentage
On the day of the peak sign   24   36.9
Within one day of the peak sign   46   77.8
Within two days of the peak sign   62   95.5
Within three days of the peak sign   64   98.5*
 

NOTE: Estimated time of ovulation was determined by hormonal assays; peak mucus symptom was determined by self-examination. *--The remaining 1.5 percent resulted from one cycle that was completely dry. Adapted from Hilgers TW. Methods of natural family planning. In: Reproductive anatomy and physiology for the natural family planning practitioner. Creighton University, Omaha, Neb., 1981:49. Used with permission.

Using a chart, couples monitor cervical mucus changes during the menstrual cycle. Daily entries include a description of mucus, as well as a stamp that correlates with the description. Postovulatory infertility begins on the fourth day after the day of the peak mucus sign. While this rule was developed empirically, the reliability of the rule has been confirmed by hormonal studies, which showed that no ovulatory events occurred more than three days after the peak mucus sign. [3],[14],[15] In the preovulatory phase, a woman is considered infertile during the days before cervical mucus begins to build. Days of menstruation, however, are considered possibly fertile because an early mucus build-up might be obscured by the menstrual flow. Special instructions have been developed for women who have a continuous or variable presence of mucus, women who have irregular bleeding and women who are breast feeding. [16],[17]

Symptothermal Method

Today, methods to predict ovulation based solely on the basal body temperature have been replaced by systems collectively classified as the symptothermal method. When using the symptothermal method, couples rely on the occurrence of the peak cervical mucus sign, as well as the rise in basal body temperature, to confirm post-ovulatory infertility [9],[10],[18-20] (Figure 3).

Some advocates of the symptothermal method advise women to watch for periovulatory signs and symptoms such as Mittelschmerz pain, changes in the cervix (determined by internal examination), low backache, abdominal bloating, vulvar swelling and intermenstrual bleeding. While none of these signs or symptoms are universally sensitive or specific for fertility or infertility by themselves, [21] advocates of the symptothermal method report that these observations give additional confidence to couples using this method. As with the ovulation method, charting is used to assist couples in determining periods of fertility and infertility.

Most symptothermal methods of natural family planning assume that preovulatory infertility ends with the first sign of mucus. In some systems, a calendar calculation may place the preovulatory period of infertility at an even earlier date than the first appearance of cervical mucus. [22]

Lactational amenorrhea Method

In recent years, a number of prospective studies of the lactational amenorrhea method have been published. In 1988, physicians and scientists met in Bellagio, Italy, to study available data for couples using the lactational amenorrhea method. The consensus of the group was that the maximum birth-spacing effect of breast feeding is achieved when a mother fully, or nearly fully, breast feeds and remains amenorrheic (not including any bleeding that occurs before the 56th postpartum day). The researchers concluded that when these two conditions are met, the contraceptive effectiveness of breast feeding may be as high as 98 percent in the first six months. [23] However, these conditions are met in only a minority of women. Since the Bellagio Conference, two studies have examined pregnancy rates among women who experienced lactational amenorrhea irrespective of the amount of breast feeding. [24],[25] In these studies, pregnancy rates of 1.7 and 2.9 percent were reported in the first six months.

Obviously, the lactational amenorrhea method is only applicable to women in a specific reproductive category for a specific period of time. Therefore, to become clinically useful in natural family planning, it will need to be incorporated into either the ovulation method or the symptothermal method. [26] While both the ovulation method and the symptothermal method have instructions for breast feeding, neither utilizes the lactational amenorrhea method at this time.

Effectiveness of Natural Family Planning Methods

Early studies established that both the ovulation method and the symptothermal method have excellent method-effectiveness ratings, with pregnancy rates no greater than 1.0 per 100 women-years under optimal circumstances. [8],[18],[22]

Slightly higher rates of unintended pregnancy (2.0 per 100 women-years for the symptothermal method, 3.0 pregnancies per 100 women-years for the ovulation method and 1.0 pregnancy per 100 women-years if intercourse is limited to the post-ovulatory period) have been reported by the U.S. Public Health Service. [27],[28]

The topic of use-effectiveness of methods of natural family planning has generated much controversy A review of studies performed over the past 15 years [29] revealed that pregnancy rates varied from 2.5 percent 12 to 27.9 percent 11 in couples who used the ovulation method and from 2.3 percent 20 to 19.1 percent 9 in couples who used the symptothermal method. A review of studies conducted before 1980 revealed a similar wide variation in use-effectiveness. [30] Careful examination of these studies suggests a number of reasons for these inconsistent data.

First, different systems of natural family planning methods were used in the studies. Therefore, not only were the actual methods different, but the way in which couples received instructions differed as well.

Second, the qualifications of instructors varied from study to study Natural family planning methods are easy to learn and easy to use, as evidenced by their successful use among some illiterate populations of undeveloped countries. [29],[31] To maximize effectiveness of these methods, however, instructions must be given by an experienced, well-qualified person. [31] Third, and most important, classification of pregnancies that occurred while using a particular method was not consistent among the studies; therefore, the actual definition of use-effectiveness was not standardized. Some studies evaluated natural family planning purely as a method of contraception and, therefore, all pregnancies that occurred were considered failures of the method. This approach is problematic because modern methods of natural family planning can be used to achieve, as well as avoid, pregnancy. Because these methods precisely define the days of fertility and infertility, it is possible for a couple to know on any given day whether conception is likely.

One standardized system, the Creighton Model Natural Family Planning System, has been developed for educating instructors, teaching couples and evaluating pregnancies. Four large prospective studies (involving 1,793 to 7,238 couple-months of use) have been conducted to evaluate this system, two of which have been published. [7],[13] Comparable results among these studies indicate that consistent data can be obtained when study variables are standardized.

Advantages of Natural Family Planning

In addition to proven effectiveness in avoiding and achieving pregnancy, natural family planning offers a number of other advantages. Because the various methods of natural family planning do not require medication, chemicals or devices, no reportable side effects or risks are involved. As a result, natural family planning is particularly useful for couples who cannot tolerate or have concerns about other methods of family planning. Indeed, studies have reported that women who practice methods of natural family planning do so for health reasons, and because the methods are natural and do not require the use of chemicals. [32],[33]

Also, these methods are relatively inexpensive. While many programs charge an instructional fee and a fee for supplies such as charts, stamps, books and thermometers, once the chosen method has been mastered, no ongoing costs are involved.

Surveys of couples who use methods of natural family planning indicate that communication in a relationship is increased, especially concerning matters of sexuality. Periods of abstinence from genital contact create opportunities for a couple to explore the emotional, intellectual and spiritual aspects of sexuality. Well-maintained symptom and basal body temperature charts provide a good record of health status. When a woman is regularly observing her signs of fertility, she is more likely to discover problems and seek treatment earlier.

Finally, because no major religions oppose methods of natural family planning, the methods are acceptable and can be used in all countries of the world.

REFERENCES

1. Katz DE Human cervical mucus: research update. Am J Obstet Gynecol 1991;165(6 Pt 2):1984-6.

 2. Hilgers TW. Coitus induced ovulation and double ovulation. In: Reproductive anatomy and physiology for the natural family planning practitioner. Omaha, Neb.: Creighton University Natural Family Planning Education and Research Center, 1981:45-6.

3. Hilgers TW, Abraham GE, Cavanagh D. Natural family planning. 1. The peak symptom and estimated time of ovulation. Obstet Gynecol 1978;52:575-82.

4. Treloar AE, Boynton RE, Behn BG, Brown BW. Variation of the human menstrual cycle through reproductive life. Int J Fertil 1970;12:77-126.

5. Chiazze L Jr, Brayer FT, Macisco JJ Jr, Parker MP, Duffy BJ. The length and variability of the human menstrual cycle. JAMA 1968;203:377-80.

6. Hilgers TW. Methods of natural family planning. In: Reproductive anatomy and physiology for the natural family planning practitioner. Omaha, Neb.: Creighton University Natural Family Planning Education and Research Center, 1981:49.

7. Doud J. Use-effectiveness of the Creighton Model of NFP. Int Rev Nat Fam Plann 1985;9:54-72.

8. Weissmann MC, Foliaki L, Billings EL, Billings JJ. A trial of the ovulation method of family planning in Tonga. Lancet 1972;2(781):813-6.

9. Wade ME, McCarthy P, Braunstein GD, Abernathy JR, Suchindran CM, Harris GS, et al. A randomized prospective study of the use-effectiveness of two methods of natural family planning. Am J Obstet Gynecol 1981;141:368-76.

10. Medina JE, Cifuentes A, Abernathy JR, Spieler JM, Wade ME. Comparative evaluation of two methods of natural family planning in Columbia. Am J Obstet Gynecol 1980;138:1142-7. 11. A prospective multicentre trial of the ovulation method of natural family planning.

Il. The effectiveness phase. Fertil Steril1981;36:591-8.

12. Thapa S, Wong MV, Lampe PG, Pietojo H, Soejoenoes A. Efficacy of three variations of periodic abstinence for family planning in Indonesia. Stud Fam Plann 1990;21:327-34.

13. Fehring RJ, Lawrence D, Philpot C. Use effectiveness of the Creighton model ovulation method of natural family planning. J Obstet Gynecol Neonatal Nurs 1994;23:303-9.

14. Billings EL, Brown JB, Billings JJ, Burger HG. Symptoms and hormonal changes accompanying ovulation. Lancet 1972;1(745):282-4.

15. Casey JH. The correlation between midcycle hormonal profiles, cervical mucus and ovulation in normal women. In: Santamaria JN, Billings JJ, eds. Human love and human life. Melbourne, Australia: Polding, 1979:68-71.

16. Billings EL, Billings JJ, Catarinich M. Billings Atlas of the ovulation method: the mucus patterns of fertility and infertility. 5th ed. Melbourne: Ovulation Method Research and Reference Centre of Australia, 1989.

17. Hilgers TW, Daly KD, Hilgers SK, Prebil AM. The ovulation method of natural family planning: a standardized, case management approach to teaching. Book one: basic teaching skills. Omaha, Neb.: Creighton University Natural Family Planning Education and Research Center, 1982.

18. Rice FJ, Lanctot CA, Garcia-Devesa C. Effectiveness of the sympto-thermal method of natural family planning: an international study. Int J Fertil 1988;33 26:222-30.

19. Barbato M, Bertolotti G. Natural methods for fertility control: a prospective study. Int J Fertil 1988;33 (Suppl):48-51.

20. Frank-Herrmann P, Freundl G, Baur S, Bremme M, Doring GK, Godehardt EA, et al. Effectiveness and acceptability of the symptothermal method of natural family planning in Germany. Am J Obstet Gynecol 1991;165(6 Pt 2):2052-4.

21. Hilgers TW, Daly KD, Prebil AM, Hilgers SK. Natural family planning. III. Intermenstrual symptoms and estimated time of ovulation. Obstet Gynecol 1981;58:152-5.

22. Roetzer J. Supplemented basal body temperature and regulation of conception. Arch Gynakol 1968;206:195-214.

23. Kennedy KI, Rivera R, McNeilly AS. Consensus statement on the use of breastfeeding as a family planning method. Contraception 1989;39:477-96.

24. Short RV, Lewis PR, Renfree MB, Shaw G. Contraceptive effects of extended lactational amenorrhoea: beyond the Bellagio Consensus. Lancet 1991; 337:715-7.

25. Kennedy KI, Visness CM. Contraceptive efficacy of lactational amenorrhoea. Lancet 1992;339:227-30.

26. Gross BA. Is the lactational amenorrhea method a part of natural family planning? Biology and policy Am J Obstet Gynecol 1991;165:2014-9.

27. U.S. Public Health Service. Counseling to prevent unintended pregnancy. Am Fam Physician 1994;50:971-4.

28. Hatcher RA, ed. Contraceptive technology. 16th rev ed. New York: Irvington, 1994.

29. Kambic RT. Natural family planning use-effectiveness and continuation. Am J Obstet Gynecol 1991; 165(6 Pt 2):2046-8.

30. Hilgers TW. A critical evaluation of effectiveness studies in natural family planning. In: Proceedings of an international symposium on natural family planning sponsored by the World Health Organization. Dublin, Ireland;1979:94-109.

31. Ryder RE. Natural family planning: effective birth control supported by the Catholic Church. BMJ 1993;307:723-6.

32. Freundl G, Frank P, Bauer S, Doring G. Demographic study on the family planning behaviour of the German population: the importance of natural methods. Int J Fertil 1988;33(Suppl):54-8.

33. Stanford JB, Lemaire JC, Fox A. Interest in natural family planning among female family practice patients. Fam Pract Res J 1994;14:237-49.

The Author

JOHN H. GEERLING, M.D. is currently practicing emergency medicine at St. John's Medical Center, Steubenville, Ohio. Dr. Geerling is a graduate of St. Louis University School of Medicine and completed a residency in family practice at St. Mary's Medical Center, Evansville, Ind. He also completed the Natural Family Planning Medical Consultant program at Creighton University School of Medicine, Omaha.

Address correspondence to John H. Geerling, M.D., Box 758, 100 Franciscan Way, Steubenville, OH 43952.

The authors acknowledge the contributions of Robert W Fisher, M.D., Thomas W Hilgers, M.D., and David Power, M.D., in the development of this manuscript.

Figures 1 and 2 provided by Thomas W Hilgers, M.D., of Omaha. Used with permission. Figure 3 provided by David Power, M.D., St. Paul. Used with permission. GRAPHIC: Photograph; Table; Graph