What is Natural Family Planning?

Natural Family Planning is based on the observation of naturally occurring signs and symptoms of the fertile phase of a woman's menstrual cycle. Couples using NFP to achieve pregnancy engage in intercourse during the woman's fertile phase. Couples wishing to postpone pregnancy simply abstain from sexual relations during the time of fertility. No drugs, devices or surgical procedures are used in the practice of NFP.  NFP reflects the dignity of the human person within the context of marriage and family life, promotes openness to life, and recognizes the value of every child. By respecting the love-giving and life-giving natures of marriage, NFP can enrich the bond between husband and wife.

NFP enhances a couples sexuality. The couple learns that true human sexuality is spiritual, physical, intellectual, creative and emotional. Couples who practice NFP testify to the importance of periodically avoiding genital contact in the growth of their overall marriage relationship. Mutual respect deepens.

Is NFP Rhythm?

NFP is not Rhythm.  The Rhythm or calendar method was in use more than 50 years ago. It was based on the theory that ovulation could be determined by calculations based on the number of days from previous menstrual cycles. This method often proved inaccurate because of the unique nature of each women's ovulation cycle: some women have very irregular cycles and almost all women have a cycle of unusual length once in a while.  Modern methods of NFP are the result of over 30 years of scientific research in human fertility. They are based on the day-to-day observations of the naturally occurring signs and symptoms of the fertile and infertile phases of the menstrual cycle. NFP methods take advantage of the changes associated with ovulation, treating each cycle as unique. NFP allows couples to adjust their behavior to the naturally occurring cycles of a woman's body. It is not a contraceptive, i.e. it does nothing to work against conception.

What are the signs of fertility?

A woman's body provides three basic ways to identify the fertile and infertile times of her cycle. Recognizing the pattern of these physical signs forms the basis for all methods of NFP.  A primary sign of fertility is the mucus released from the woman's cervix. A woman learns to identify the normal, healthy, cervical mucus which indicates the days that intercourse is most likely to result in a pregnancy. This is simply done by looking and touching the external secretions that come from the vagina. The second sign is her basal body temperature. Due to hormonal activity, a woman's resting temperature changes during the menstrual cycle. Lower temperatures indicate that ovulation has not yet occurred. Higher temperatures indicate a rise in progesterone which signals the end of the fertile time. The third sign of fertility is the change in the shape or texture of the cervix.

How does NFP work?

Understanding that intercourse during the fertile time can result in pregnancy , couples using the natural methods must be clear regarding their family planning intention- that is, do they wish to achieve or postpone pregnancy?  If a couple wishes to achieve pregnancy, they have intercourse during the fertile time. If a couple wishes to postpone or avoid a pregnancy, they abstain from intercourse and any genital contact during the fertile time.

How effective are the methods of natural family planning?

When couples are taught by competent teachers and follow the rules of the methods precisely, NFP is highly successful in achieving the intended family plan. Studies, including one by the U.S. government, have shown that some NFP methods can be used at the 99% level of effectiveness for avoiding pregnancy. That is equal to the birth control pill and far better than all the barrier methods.

Effectiveness of Natural Family Planning in postponing pregnancy can be measured by the number of pregnancies among 100 couples in one year using periodic abstinence.  When couples are taught well, understand the method, are clear about family planning intention, and carefully follow all the rules for avoiding pregnancy they can expect the following:

NFP Method Effectiveness (Number of unplanned births) Measurements
Ovulation Method: 


Cervical Mucus
Sympto-thermal method


Cervical Mucus and Temperature
Post ovulation:


Mostly temperature

Reference: Contraceptive Technology, 17th Revised edition. Robert A. Hatcher,
Irvington Press: New York 1998.