At its core, Natural Family Planning (NFP, also known as green sex or fertility awareness) is really about understanding how the female body works. Adult women are constantly undergoing cycles of fertility which have observable, physical signs that can be tracked to determine the times of fertility and infertility. Methods of NFP provide the tools with which to track these signs in order to achieve or postpone a pregnancy.

Though often used in religious communities, fertility awareness methods are a good choice for women regardless of faith background. Anyone who wants to prevent or achieve pregnancy completely naturally and chemical-free is a good candidate. Many users of these methods report benefitting greatly from the empowerment afforded simply by understanding how the amazing female body truly works.

How NFP Works   

Natural Family Planning uses a variety of physical signs (depending on method) to determine fertile windows. There are several different modern effective methods of NFP. Each identifies the most fertile time in a woman’s cycle and informs the couple to abstain from sexual intercourse during that time if they wish to avoid conception.

The Marquette Method, developed at Marquette University, uses biomarkers (namely, the ClearBlue Fertility Monitor, which assesses hormone levels) often in conjunction with other fertility observations like cervical mucus or basal body temperature to determine the fertile window. 

The Billings Method uses observations about cervical mucus exclusively to determine fertility.

The Creighton Model is a modified version of the Billings Ovulation Method that uses observations about cervical mucus and bleeding to determine fertility.

The Sympto-Thermal Method relies on three key observations: cervical mucus, basal body temperature, and changes in the cervix. It is more effective and more complex than observation-only methods.

The Standard Days Method is a new method of NFP developed by the Institute for Reproductive Health at Georgetown University. It does not use observations or temperature. It is an updated calendar method for women with very regular cycles. The couple abstains from sexual intercourse on days 8 through 19 of each cycle; cycles begin on the first day of her period, and cycles must be from 26 to 32 days in length.

The Two-Day Method, also developed at Georgetown, uses observations and a simple two-day rule. It is easier to learn than the Billings or Creighton methods, but somewhat less effective.

“Natural Cycles” is the only FDA  approved contraceptive and is considered "green". This NFP tool is an app powered by an algorithm that determines your fertility status based on body temperature.

Ecological Breastfeeding or the Lactational Amenorrhea Method is only used by mothers who are breastfeeding a baby. Breastfeeding naturally delays ovulation (in most cases). These methods provide ways for a mother to track whether fertility has returned following delivery. It is the only NFP method that does not require periodic abstinence.

Most methods of NFP have communities (including Facebook groups) and local teachers who can help guide new users. Visit the links above to find an instructor near you.

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Effectiveness of NFP

The effectiveness of any fertility-awareness based method varies from one couple to another, just like any type of “birth control.” All NFP methods are significantly less effective for couples who do not follow the rules of the method.

All NFP effectiveness percentages refer to couples who practice the method correctly and strictly. Different studies show different degrees of effectiveness; there is no single exact number to cite. A 95% method effectiveness would mean that 5 out of 100 women practicing the method correctly for one year will get pregnant. Individual effectiveness varies.

The Marquette Method: 98-99% effective (reference)
The Sympto-Thermal Method: ~99% effective (reference)
The Creighton Method: >98% effective (reference)
The Billings Method: >97% effective (reference)
Two-Day Method: ~96% (reference)
Standard Days Method: ~95% (reference)
Ecological Breast-Feeding (LAM): ~94% effective (reference)