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BMJ. 1993 Sep 18;307(6906):723-6.

"Natural family planning": effective birth control supported by the Catholic Church.

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  • 1Department of Endocrinology, Dudley Road Hospital, Birmingham.


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 the efficacious among people in areas of poverty.


The Catholic Church approves the use of natural family planning (NFP) methods. Many people think only of the rhythm method when they hear NFP so they perceive NFP methods to be unreliable, unacceptable, and ineffective. They interpret the Catholic Church's approval of these methods as its opposition to birth control. The Billings or cervical mucus method is quite reliable and effective. Rising estrogen levels coincide with increased secretion of cervical mucus, which during ovulation is relatively thin and contains glycoprotein fibrils in a micelle like structure aiding sperm migration. Ultrasonography confirms that the day of most abundant secretion of fertile-type eggs white mucus is the day of ovulation. Once progesterone begins to be secreted, cervical mucus becomes thick and rubbery and acts like a plug in the cervix. Other symptoms associated with ovulation include periovulatory pain and postovulatory rise in basal body temperature. A WHO study of 869 fertile women from Australia, India, Ireland, the Philippines, and El Salvador found 93% could accurately interpret the ovulatory mucus pattern, regardless of education and culture. The probability of pregnancy among women using the cervical mucus method and having intercourse outside the fertile period was .004. The probability of conception increased the closer couples were to the fertile period when they had intercourse (.546 on -3 to -1 peak day and .667 on peak day 0), regardless of education and culture. The failure rate of NFP among mainly poor women in Calcutta, India, equal that of the combined oral contraceptive (0.2/100 women users yearly). Poverty was the motivating factor. NFP costs nothing, is effective (particularly in poverty stricken areas), has no side effects, and grants couples considerable power to control their fertility, indicating the NFP may be the preferred family planning method in developing countries. Prejudices about NFP should be dropped and worldwide dissemination of NFP information should occur.

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