On August 10, 2018 FDA granted approval to Natural Cycles as a software application for contraception. This marks the first time the FDA has approved a fertility charting medical device for use as a contraceptive. Previous devices have been approved as aids to conception but carried the caution they are not to be used for contraception (even though many users ignored this). Natural Cycles has the following indication:
Natural Cycles is a stand-alone software application, intended for women 18 years and older, to monitor their fertility. Natural Cycles can be used for preventing a pregnancy (contraception) or planning a pregnancy (conception).
How it works
Natural Cycles is an app with a proprietary algorithm that uses daily basal body temperatures to determine the fertile window. In contrast to the older temperature-only methods that only identified infertility after ovulation, Natural Cycle developers claim they can identify infertile days prior to ovulation as well.
The developers of Natural Cycles have published clinical studies of effectiveness when used to avoid typical use unintended pregnancy rates were 8.3 percent while perfect use rates were 1 percent. However, follow-up to confirm pregnancy in all users who stopped the study early was less than complete, and a more conservative analysis that assumed all of the unknowns were pregnant yielded a potential typical use unintended rate of 9.8 percent. These typical-use rates are comparable to those of oral contraceptives. Yet, the method used in Natural Cycles is effective.
Natural Cycles and CycleProGo
How Natural Cycles compares to CCL’s CycleProGo (CPG) remains largely unexplored. In a preliminary study to be presented in September, both CPG and Natural Cycles were used to interpret 240 complete cycles recorded in the CPG database (i.e.,12 cycles from 20 separate accounts). From a CCL standpoint, this comparison raises some questions: In a significant proportion of cycles the Natural Cycles app declared a cycle day as infertile when CPG defined that day as fertile. With Natural Cycles, 25 percent of cycles had the end of Phase I three or more days later than CPG, and 22 percent of cycles had Phase III starting on or before Peak Day. This might imply the low unintended pregnancy rates from the Natural Cycles clinical study was helped by unreported barrier use during the fertile time.
What this means for NFP
Setting aside the temptation to argue the merits of CPG compared to Natural Cycles, this approval marks an important shift in the landscape for NFP in the U.S. The FDA’s approval of this app as a medical device and acknowledging it can be used to both avoid and conceive is a major step forward for the long-term goal of getting NFP methods accepted broadly in the medical community. Further, since Natural Cycles is a for-profit company and has been successful in generating investment capital from their prior European approval, we can anticipate much more advertising of fertility awareness to persons that organizations like CCL could never reach.
Should the FDA decide to act, this approval could also mean the beginning of much more scrutiny of other apps making similar claims and possible FDA actions. The large charting apps like Glow, Kindara and Fertility Friend, are now potentially at risk of making medical claims (i.e., being able to avoid pregnancy) without approval. Enforcement is totally up to FDA however, and given there are many more serious issues FDA deals with ̶̶ from food borne illnesses to drugs that have lethal side effects ̶ the landscape for these apps may not change much beyond an important new competitor with significant legitimacy. Time will tell.
When the questions arise
What should a CCL teacher or STM user say about Natural Cycles if asked?
First, acknowledge that Natural Cycles is a clinically proven fertility awareness method, while acknowledging that it was developed and sold with the option to use barriers rather than abstinence in the fertile time. Next, explain that it is a temperature-only method and many NFP users like the multiple fertility signs the Sympto-Thermal Method brings. Further, the manufacturer has not disclosed details on how it uses temps to define the fertile window, but they do have clinical testing that shows typical-use effectiveness is comparable to that of oral contraceptives. Lastly, remind them Natural Cycles is only an app, not a method, so the only source of assistance for questions about a cycle is to search the online forum for help.
— Michael Manhart, Ph.D. is CCL’s Science Advisor.