From the Guidelines
Natural Cycles is a digital fertility awareness-based method of birth control that uses a mobile app and basal body temperature measurements to predict fertile and non-fertile days, with an effectiveness rate of about 93% with typical use and 98% with perfect use. This method works by identifying the temperature rise that occurs after ovulation, as progesterone increases body temperature by 0.2-0.5°F 1. Users take their temperature each morning upon waking and enter it into the app, which uses an algorithm to identify ovulation and determine when pregnancy is possible. The app displays red days (when you should abstain or use protection) and green days (when pregnancy is unlikely).
Key Considerations
- Natural Cycles requires consistent daily temperature readings and tracking of menstrual periods for accuracy.
- This method is most suitable for women with regular cycles who can commit to daily temperature tracking and are comfortable with either abstaining or using barrier methods during fertile days.
- Users should be aware that factors like illness, alcohol consumption, or irregular sleep can affect temperature readings and reduce reliability.
- Natural Cycles doesn't protect against STIs, and the correct and consistent use of condoms is recommended if there is a risk of STI/HIV transmission 1.
Limitations and Precautions
- Women with irregular vaginal bleeding or vaginal discharge should not use Natural Cycles, as these conditions can make fertility awareness-based methods unreliable 1.
- The use of certain drugs that affect cycle regularity, hormones, and/or fertility signs may also impact the effectiveness of Natural Cycles, and a barrier method should be offered until the degree of effect has been determined or the drug is no longer being used 1.
- Chronic diseases that elevate body temperature can make basal body temperature difficult to interpret, and temperature-based methods like Natural Cycles may not be suitable for women with chronically elevated temperatures 1.
From the Research
Definition and Overview of Natural Cycles
- Natural Cycles is a fertility awareness-based method of birth control that uses a mobile application to identify a woman's ovulation day and fertile window 2, 3.
- It is based on the principle of tracking basal body temperature, ovulation test results, and date of menstruation to determine the fertile period 3.
- The method is designed to be used as a natural form of birth control, providing an alternative to hormonal or invasive methods 2, 4.
Effectiveness of Natural Cycles
- The effectiveness of Natural Cycles varies depending on the user's previous contraceptive choice and adherence to the method 5.
- Studies have reported a typical use effectiveness of Natural Cycles, with a 1-year Pearl Index (PI) ranging from 6.2 to 8.1 2, 5.
- Perfect use of Natural Cycles has been reported to have a PI of 2.0 2.
- The method has been shown to be effective in identifying a user's ovulation day and fertile window, with a low rate of false attribution of non-fertile days to the fertile window 3.
Comparison with Other Contraceptive Methods
- Natural Cycles is often compared to other fertility awareness-based methods (FABMs) and hormonal contraceptives (HCs) 4.
- FABMs, including Natural Cycles, are considered a valid alternative for women who cannot or do not want to use hormone therapy, but may have a higher failure rate if not used appropriately 4.
- HCs are commonly used and have a low rate of adverse events when used appropriately, but may have concerns about side effects 4.
User Demographics and Satisfaction
- Studies have reported that users of Natural Cycles are typically women aged 30 years or older, with a body mass index of 24, and in a stable relationship 2.
- The method has been shown to be popular among women who are planning a pregnancy in the coming years and want to learn about their individual menstrual cycle 2.