The Science Behind Using the Fertility Awareness Method to Avoid Pregnancy

Guest Blogger: Joshua Klein, MD

(Joshua U. Klein MD is Assistant Clinical Professor of OB/GYN – Mt. Sinai School of Medicine, and Medical Director at Reproductive Medicine Associates of New York — Brooklyn Office)

Although fertility charting is most popular among women who are trying to conceive, it can also be used to avoid pregnancy.

Using the Fertility Awareness Method to avoid pregnancy is predicated on four basic principles, all of which are strongly rooted in scientific evidence.

1. Conception can/will occur only during the “Fertile Window”

The relationship between menstruation and female fertility has been recognized for thousands of years; but surprising as it may seem, we have only achieved a thorough scientific understanding of the timing of ovulation and how it relates to conception and fertility in the past twenty years. Groundbreaking studies led by the NIH and published in the New England Journal of Medicine and elsewhere proved the existence of a “Fertile Window”: there are several days surrounding the time of ovulation during which it is possible to conceive. Achieving pregnancy outside of the Fertile Window has never been documented. (Ref. 1)

2. The Fertile Window can be detected in a highly accurate manner

The Fertile Window revolves around ovulation but is also dependent on dramatic hormonal changes that are necessary for ovulation to occur. Evidence of these events can be detected through a wide variety of methods, including basal body temperature measurements, cervical fluid assessment, and more formal tests of various body fluids, such as blood, urine, and saliva. While the accuracy and effectiveness of each method varies, there is essentially unanimous agreement among physicians, scientists, and other experts that using one (or more) of these methods, it is possible to detect the presence of the Fertile Window. (Ref. 2)

3. Refraining from unprotected intercourse during the Fertile Window will help women who don’t want to get pregnant prevent unintended pregnancy.

“Fertility Awareness” is the concept of using knowledge of the Fertile Window and its timing to prevent unintended pregnancy. The history of contraception based on Fertility Awareness is long and uneven; it has included many versions of the Rhythm or Calendar method, Temperature methodBillings/ovulation method, and many others. Studies aiming to clarify the effectiveness of the various methods have been inconsistent in their method and study populations, and not surprisingly, in their results. (Ref 3.) An objective analysis of the literature demonstrates the following:

a) When women are given the opportunity to follow the method correctly, it is a highly effective form of contraception, on par with some forms of medical/hormonal birth control (<1% pregnancy rate per year with perfect use, 1-2% with actual use in the largest and best available prospective study – Ref. 4)

b) Compliance and adherence have been the major limitations to long-term effectiveness of contraception based on Fertility Awareness. The effectiveness of Fertility Awareness will increase amongst a self-selected, highly motivated population (Ref. 5)

4. Engaging in unprotected intercourse during the Fertile Window will increase the chance of conception in women who want to get pregnant

Simple logic dictates that knowing when the Fertile Window occurs should help couples focus their efforts at conception and improve the efficiency with which they conceive. Indeed, this is borne out in scientific studies. Women conceive faster when they are using a monitor to help identify the Fertile Window. (Ref 6) Furthermore, on any given day of the cycle, there is a higher chance of conception if the cervical mucus predicts that the Fertile Window is “open.” (Ref 7)

In summary:

There is strong scientific evidence that Fertility Awareness can facilitate highly effective approaches to conception and contraception in a motivated population. A system such as Kindara that will reduce or eliminate barriers to compliance and adherence will lead to outcomes as good or better than those previously achieved in the best available scientific studies.


1. Wilcox et al. New England Journal of Medicine 1995; 333:1571-1521.2. Stanford et al. Obstetrics and Gynecology 2002; 100:1333-1341.3. Grimes et al. Contraception 2005; 72:85-90.4. Frank-Herrman et al. Human Reproduction 2007; 22:1310-1319.5. Freundl et al. The European Journal of Contraception and Reproductive Health Care 2010; 15:113–123.6. Robinson et al. Current Medical Research and Opinion 2007; 23:301–306.7. Bigelow et al. Human Reproduction 2004; 19:889-892.

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