The Next Generation of Natural Family Planning

Lilian White, MD
Posted on June 17, 2024

More than 40% of pregnancies in the United States every year are unintended. Reducing the number of unintended pregnancies is a Healthy People 2030 goal. Discussions regarding birth control methods are therefore an integral role of the family physician.

The most common form of contraception is female sterilization (18%), followed by oral hormonal contraceptive pills (14%). Natural family planning (NFP) is a form of family planning that uses knowledge about the female menstrual cycle to prevent unintended pregnancy or improve the likelihood of achieving pregnancy. It is estimated that less than 1% of women use natural family planning or fertility awareness–based methods; however, 1 out of every 5 women express interest in the use of NFP methods. Benefits from use of NFP methods include knowledge about a person’s menstrual cycle (to achieve or avoid pregnancy, treat infertility, and aid in the diagnosis of common women’s health concerns), lack of disruption of normal physiology, and avoidance of adverse effects associated with other forms of contraception.

In the past, NFP largely required close monitoring and tracking of signs by patients to determine the window in which they could be fertile. During the fertile window, unprotected sex is avoided to prevent conception. Various methods of NFP (e.g., symptothermal method, cervical mucus monitoring) are used, and effectiveness depends on the form used. With perfect and typical use, NFP methods as a group have been estimated to be as effective as hormonal contraception (99% and greater than 90%, respectively); however, some would criticize these statistics as being overestimates and report up to 75% effectiveness with typical use. The latter statistic is derived from the National Survey of Family Growth, which pooled patient recall data for all natural methods, rather than reporting on individual NFP method effectiveness rates.

We are beginning to see a rise in technology to support and refine NFP. Natural Cycles is the only U.S. Food and Drug Administration–cleared app and regulated medical device for the purpose of supporting NFP. The app uses information from a person’s body temperature and prior menstrual cycles to provide information to the user on their predicted fertility. Over time, the app personalizes and refines the user’s window of fertility. It is initially more conservative, with a wider window of estimated fertility that potentially narrows with continued use of the app. This is an improvement on some previous methods of NFP (e.g., some calendar-based methods), which assumed a 26- to 32-day cycle for all users. The Natural Cycles app has been found to be 98% effective with perfect use (i.e., when the app is used perfectly) and 93% effective with typical use (i.e., some user error is involved). Many other apps are marketed for NFP with varying reliability and effectiveness.

NFP methods, including the Natural Cycles app and similar apps, are not recommended for patients in whom pregnancy would pose an unacceptable health risk and do not prevent against sexually transmitted infections. However, with advances in technology and research, these methods provide more detailed information about the hormonal cycle, which can empower women to monitor their health and facilitate the diagnosis and treatment of common conditions, effectively serving as a vital sign of health.