British Medical Journal: NFP

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“Natural family planning”:
Effective Birth Control Supported by the Catholic Church

British Medical Journal, Sept 18, 1993 v307 n6906 p723(4)

 R.E.J. Ryder.


Natural family planning, when used by motivated couples, is a safe and cost-effective means of birth control. Natural family planning, which involves teaching women to recognize signs of ovulation and to avoid intercourse on fertile days, is the only method of birth control approved by the Catholic Church. A total of 869 women of diverse ethnic and economic backgrounds participated in a study conducted by the World Health Organization. Regardless of literacy and culture, 93% of the women were able to recognize the changes in their cervical mucus associated with ovulation. Other studies have emphasized the importance of good initial teaching and the motivation of the woman practicing the method. A failure rate of 0.2 pregnancies per 100 women was found in a study of 19,843 women in India.

[Full Text: COPYRIGHT 1993 British Medical Association]

During 20-22 September Manchester is to host the 1993 follow up to last year’s “earth summit” in Rio de Janeiro. At that summit the threat posed by world overpopulation received considerable attention. Catholicism was perceived as opposed to birth control and therefore as a particular threat. This was based on the notion that the only method of birth control approved by the church–natural family planning–is unreliable, unacceptable, and ineffective.

In the 20 years since E L Billings and colleagues first described the cervical mucus symptoms associated with ovulation natural family planning has incorporated these symptoms and advanced considerably. Ultrasonography shows that the symptoms identify ovulation precisely. According to the World Health Organisation, 93% of women everywhere can identify the symptoms, which distinguish adequately between the fertile and infertile phases of the menstrual cycle. Most pregnancies during trials of natural family planning occur after intercourse at times recognised by couples as fertile. Thus pregnancy rates have depended on the motivation of couples. Increasingly studies show that rates equivalent to those with other contraceptive methods are readily achieved in the developed and developing worlds. Indeed, a study of 19,843 poor women in India had a pregnancy rate approaching zero. Natural family planning is cheap, effective, without side effects, and may be particularly acceptable to and efficacious among people in areas of poverty.

The 1993 follow up to last year’s “earth summit” in Rio de Janeiro is to take place in Manchester during 20-22 September and is entitled “Partnerships for change.” The Rio earth summit focused considerable attention on the expanding population of the world as an important issue in relation to resources, environment, and poverty. In the media the “opposition of the Catholic Church to birth control” was discussed (BBC Radio 4, Today Programme, 18 May 1992) and considered to be an important factor with the many millions of Catholics in the world, particularly the Third World, such as Brazil. In the medical press the “Pope’s continuing opposition to birth control” was condemned[1] and powerful Vatican opposition was considered likely to wreck hope of useful progress at the earth summit with regard to global overpopulation as a most urgent ecological hazard.[2]

The widespread beliefs that the Catholic Church is opposed to birth control,[1] that the urgent provision of artificial contraception within the Third World is the only answer to overpopulation, and that the Catholic Church is opposed to this[2] all stem from the perception that the so called “natural methods of family planning,” which are approved by the Catholic Church, are unreliable, unacceptable, and ineffective. Historically, this perception is based on the unreliability of the rhythm method of contraception (“Roman roulette”), which attempts to identify the fertile phase of the woman’s cycle by calendar calculations. Is this perception as accurate today as it may have been in the past?

The ovum has a life span of not more than 24 hours and is fertilisable for only part of that time.[3] The life span of the sperm may be measured in hours under adverse conditions. Under optimum conditions, however, sperms may remain viable for four or five days, and a life span of up to seven days has been postulated.[3] Thus a woman is potentially fertile for no more than six to eight days of her cycle, probably less in most cases. To what extent can these potentially fertile days be accurately identified and avoided by most women as a method of birth control?

Cyclical changes in cervical mucus secretion

In 1972 Billings et al reported the characteristic changes in cervical mucus secretion which occur during the menstrual cycle.[4] After menstruation there are a variable number of “dry” days with little or no mucus secretion and a feeling of dryness in the vaginal area. Then, as ovulation approaches under the influence of increasing oestrogen concentrations[3 5] the dry feeling ends and there is increasing secretion of cervical mucus, which at the time of ovulation becomes an abundant discharge of substance like the raw white of an egg. After ovulation the first secretion of progesterone abruptly reverses the effect of oestrogen on cervical mucus and causes it to become thick and rubbery, forming a plug in the cervix.[3 5] The fertile-type, “raw egg white” cervical mucus is of low viscosity and high threadability (spinnbarkeit) with glycoprotein fibrils in a micelle-like structure which aids sperm migration. It contains sugars and trace elements necessary for sperm survival, capacitation, and transport and it can maintain the sperm capable of fertilisation for several days.[3 5 6] By contrast, the thick, white, non-stretchy mucus which occurs at other times in the cycle is impenetrable by sperm and hostile to its survival.

Other symptoms have been described in association with ovulation, in particular periovulatory pain and the progesterone induced postovulatory rise in basal body temperature. Hormonal studies have confirmed the close relation of the various symptoms with ovulation,[4 7] and more recently ovarian ultrasonography has suggested that the day of most abundant secretion of fertile-type egg white mucus identifies the day of ovulation as precisely as does the luteinising hormone peak (see figure).[8] Other symptoms associated with the cyclical changes in oestrogen and progesterone concentrations include changes in the cervix, breast tissue, skin, hair, libido, and moods.[3 5]

Pregnancy and contraception

Reported pregnancy rates (pregnancies per 100 woman years; Pearl index) in well motivated couples using the condom, diaphragm, intrauterine device, and progestogen only and combined oestrogen-progestogen oral contraception are 3.6, 1.9, 1.4, 1.2, and 0.18 respectively.[9] Much higher rates have been recorded, particularly among less motivated couples–for example, pregnancy rates of 21 and 22 in condom users[10] and 23 in diaphragm users.[10] Pregnancy rates of 23 and 28 have also been reported in users of oral contraceptives in the developing world.[11] As shown in Oxford, even the contraceptive pill may fail if the woman forgets to take it, runs out of tablets, or has diarrhoea and vomiting or other illness.[12]

Early trials of birth control based on symptom observation[13-17] yielded pregnancy rates of 6.0[17] to 25.4.[13] Most conceptions occurred because of intercourse on days designated by the family planning method as fertile. Controversy therefore ensued[18-21] between those who thought that all pregnancies occurring in trials should be considered as failures of the particular method[19 21] and those who thought that the method could not be blamed if couples had intercourse during a phase which they knew to be fertile.[18 20] It was also possible that initial scepticism about natural family planning methods led to a casual approach by couples.[13]

WHO study

Given a natural pregnancy rate–that is, the Pearl index without any birth control–estimated as 80,[22] the cheapness of natural family planning, and the acceptability of natural family planning to many cultures and religions, the World Health Organisation undertook an international study.[23-27] A total of 869 women of proved fertility and widely varying cultural, educational, and economic backgrounds were studied in five centres (Auckland, Bangalore, Dublin, Manila, and San Miguel, El Salvador). Regardless of culture and education, 93% of the women recorded an interpretable ovulatory mucus pattern. Of the El Salvador women, 48.1% were illiterate and yet recognised the mucus symptoms.[23]

Detailed analysis in the WHO study confirmed the potential effectiveness of mucus symptom observation as a means of family planning. The probability of conception from intercourse outside the period of fertility defined by cervical mucus observation was 0.004 (see table).[25] Intercourse on days designated as fertile by cervical mucus observation resulted in conception with increasing frequency the nearer to ovulation that intercourse occurred, intercourse on the peak day of cervical mucus secretion resulting in a probability of conception of 0.667 (table).[25] Thus it is clear that women of all cultures and educational backgrounds can learn to recognise when they ovulate and when they are potentially fertile and that if intercourse is avoided on potentially fertile days pregnancies will not occur.


Increased confidence in natural contraception

After the early studies,[13-17] increased confidence in and experience with natural family planning methods tended to lead to progressively lower overall pregnancy rates. The rates, however, remain variable, depending on the standard of teaching and the motivation to avoid pregnancy.[24 28-39] A study in Chile confirmed the importance of good initial natural family planning teaching, experienced teachers achieving a pregnancy rate of 4.7, inexperienced teachers achieving a rate of 16.8.[28] Studies have underlined the importance of motivation, one international study finding a pregnancy rate of 4.13 in couples wishing to limit their families but a rate of 14.56 in couples wishing only to space their families.[29] Studies suggest that methods combining several indicators of ovulation yield lower pregnancy rates.[3] The cost issue has been addressed, studies from Liberia and Zambia showing pregnancy rates of 4.3 and 8.9 and user costs of $40 and $30 respectively.[35] A study of natural family planning in general practice in the United Kingdom also found it to be by far the cheapest method.[39]

The largest natural family planning study combined effective teaching with high motivation and showed that natural family planning can be extremely effective in the Third World.[33] The study was of 19 843 predominantly poor women in Calcutta, 52% Hindu, 27% Muslim, and 21% Christian. Because of poverty motivation was high both among the users and among the well trained teachers of natural family planning. The failure rate was similar to that with the combined contraceptive pill–0.2 pregnancy/100 women users yearly.[33] The result suggests that poverty as the motivation can greatly improve the effectiveness of natural family planning. A similar result, however, was achieved in Germany in a study with a pregnancy rate of 0.8.[34]

An Italian study found an overall pregnancy rate of 3.6, all the pregnancies occurring in couples wishing to space but not limit their families. The pregnancy rate was zero in couples who wanted no more children.[30] With other German studies finding pregnancy rates of 1.8[31] and 2.3,[36] a study in general practice in the United Kingdom finding a rate of 2.7,[39] and a study among 3003 illiterate and semiliterate women in India yielding a pregnancy rate of 2.04[37] the accumulating data confirm that natural family planning can be as effective as any method of family planning.

Implications for the Third World

In the WHO study most couples in the three developing countries who practised natural family planning were satisfied with the frequency of intercourse, whereas in the two developed countries one third of subjects and half of their partners who practised the method would have preferred more frequent intercourse.[27] It might be argued that natural family planning being cheap, effective, without side effects, and potentially particularly effective and acceptable in areas of poverty may be the family planning method of choice for the Third World. The case for and against this may be argued and debated, but whatever the standpoint there is no doubt that it would be more efficient for the ongoing world debate on overpopulation, resources, environment, poverty, and health to be conducted against a background of truth rather than fallacy. It is therefore important that the misconception that Catholicism is synonymous with ineffective birth control[1 2] is laid to rest.

Understanding the simple facts about the signs of fertility confers considerable power to couples to control their fertility, for achieving as well as preventing conception. The widespread dissemination of these simple facts would be useful everywhere but might be of particular value in the Third World.


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