You may have heard that Natural Cycles was given the green light by the FDA last week to market itself as an official contraceptive. Natural Cycles predicts when a user can/cannot become pregnant based on that user inputting their daily basal body temperature reading.

Understandably, the internet has been abuzz with proponents and sceptics alike debating the wisdom of approving such an app, while women in their hundreds have been chiming in with anecdotal experiences, both negative and positive.

However, after almost two years of tracking my own fertility to avoid pregnancy with the Symptothermal Method (cervical fluid and basal body temperature), you won’t find me recommending women to use an app such as Natural Cycles as their sole form of contraception.

Curious as to why? Below you’ll find the seven key reasons that I don’t personally recommend Natural Cycles to the women in my life.

1.) Using your basal body temperature (BBT) fluctuations to track when you are/are not fertile is not new.

It was first discovered by Dr William Squires in 1868 in a London tuberculosis sanatorium that the BBT of fertile women seemed to rise in the second half of their menstrual cycle. This was also noticed around the same period by Dr Mary Putnam Jacobi in Philadelphia; however, neither Squires nor Jacobi realised that this biphasic pattern was related to ovulation. It wasn’t until 1904 that Dutch gynaecologist Theodoor Hendrik van de Velde in Holland discovered that the rise was related to the event of ovulation. In 1928 he confirmed that it was due to the thermogenic effect of the hormone progesterone which is secreted by the corpus luteum after ovulation.

Also during the 1920s, Japanese gynaecologist Dr. Kyusako Ogino and Austrian obstetrician-gynaecologist Dr Herrmann Knaus were separately conducting research on ovulation and the timing of fertile days during the menstrual cycle. The Ogino-Knaus system was the precursor for the calendar rhythm method, which was publicised to American women in 1932 by Dr Leo Latz with the publication of his book The Rhythm of Sterility and Fertility in Women. Unfortunately, many of Latz’ fellow doctors were unhappy with this information being made available to the public and he was dismissed from the faculty of the Loyola University School of Medicine.

Fast-forward to 1935 and the research on both BBT and calendar/rhythm was eventually harnessed by a German Catholic priest called Father Wilhelm Hillebrand who was trying to help some of his parishioners who had serious health reasons to avoid a pregnancy. He at first advised his parishioners to use the Ogino-Knaus calendar/rhythm system; however, when three of the women fell pregnant almost immediately, Father Wilhelm Hillebrand went in search of better options and came across van de Velde’s research on BBT. He decided to combine BBT observations with the Ogino-Knaus calendar calculations and the Calculo-Thermal method was born.

Then, in the late 1940’s and 50’s, the cyclical changes in cervical mucus and their relationship to ovulation started to receive more attention. While cervical mucus had first been described in 1855 by London doctor W. Tyler Smith, nobody thought to link the changes in mucus to cyclic changes in fertility – cervical mucus was then promptly forgotten about for the next 100 years! However, this all changed in the late 1940s and 50s when a number of scientists revisited the role of cervical mucus in fertility (Erik Odeblad and John and Evelyn Billings being some of the more well-known). Around the same time, in 1953 New York obstetrician-gynaecologist Dr Edward F Keefe added daily mucus observations to the Calculo-Thermal method, and the Symptothermal Method was born. The Symptothermal Method was then further developed and promoted by Dr. Konald A Prem in America, and Dr Jozef Roetzer in Austria.

PHEW. This point turned into an essay but the gist of it is this: the temperature method of fertility awareness has been around since 1935 and was superseded by the more reliable Symptothermal Method (Cervical fluid + BBT) in 1953.

2.) Natural Cycles doesn’t appear to be a very conservative temperature-only method of Fertility Awareness.

One of the pioneers of the temperature-only method of Fertility Awareness was a German doctor called Gerhard K. Doering who released research in 1967 that highlighted the importance of

1. Waiting until the evening of the third raised temperature, due to the fact that he documented a number of pregnancies where conception occurred from intercourse on the second raised temperature. This was also to ensure that the rise was not due to a fever or disturbance.
2. Using a rule (now known as the Doering Rule) to calculate the last “infertile” day after menstruation, based on the earliest thermal shift recorded during the last 12 consecutive cycles.

Unfortunately, I have seen a number of Natural Cycles charts where green days are given on the second raised temp, and green days are given that extend beyond where a Doering rule would have cut them off. This places the unsuspecting user at risk of unintended pregnancy (and unfortunately I have seen some of those pregnancy charts, too).

3.) Basal body temperature only rises AFTER you’ve ovulated. Taking your temperature every morning will not warn you that ovulation is approaching – this is especially dangerous if you experience an ovulation that occurs unexpectedly earlier than usual.

Cervical fluid is more important than BBT in the follicular phase because it is the only physiological sign (apart from cervical changes) that is affected by oestrogen. Oestrogen increases as ovulation approaches. In short, Natural Cycles cannot predict or protect you from an early ovulation, and nowhere have I seen them mention this in any marketing materials. You would need to be checking your cervical fluid every day (and using some form of Doering rule) to safeguard against an unexpectedly early ovulation.

4.) Natural Cycles’ marketing materials don’t seem to mention that their app is not suitable for women WHO WOULD BE DEVASTATED BY AN UNINTENDED PREGNANCY.

If you visit the practitioner section of the Natural Cycles website, a flowchart advises that GP’s should direct these women to choose an IUD instead. Elina Berglund, the original creator of Natural Cycles and previous CERN physicist says that the ideal user “is a woman in a stable relationship who is planning to have children at some point, and who would like a break from hormonal contraception ahead of trying.” Kristina Gemzell Danielsson is a professor in obstetrics and gynaecology at Karolinska Institutet and is one of the research scientists behind the Natural Cycles studies. She is quoted as saying that Natural Cycles is “not a good option for women who absolutely want to avoid a pregnancy”.

5.) Natural Cycles SAYS that they are more effective than other Fertility Awareness-Based Methods.

The abstract of the most recent Natural Cycles study states “This study shows that the efficacy of a contraceptive mobile application is higher than usually reported for traditional fertility awareness-based methods”. I guess this really comes down to semantics. What do you class as a “traditional” method of Fertility Awareness? I can certainly understand how Natural Cycles should be more effective than the Rhythm Method (calendar only), however that’s not exactly a high standard to beat! Moreover, it has been proven that using a Symptothermal Double-Check Method (cervical fluid, BBT and a calendar-based rule such as the Doering rule) is more effective than a single-check method (temp-only or cervical mucus-only). I have also seen on a number of occasions Natural Cycles quoting statistics from the CDC to ensure that their own statistics look incredibly effective in comparison to other FABM’s. The CDC unfortunately are required to lump together all FABM methods when calculating typical-use efficacy rates – this means that the high efficacy rate of the Symptothermal Method is obscured by the inclusion of the Rhythm method. You can read more about that on the FACTS website here: https://www.factsaboutfertility.org/petition-the-cdc-women-and-medical-professionals-need-accurate-information/

6.) Just because the FDA approved Natural Cycles, doesn’t mean I’LL BE leaping off MY seat to purchase a subscription.

Let’s not forget that the FDA also approved controversial permanent contraceptive implant Essure, which is now the subject of class action lawsuits and over 27,000 complaints of injury (many serious and irreversible). I’ll be taking this approval with a grain of salt.

7.) Natural Cycles only gives their users half of the picture.

When Natural Cycles uses language like “the app does the work for you and tells you exactly when to use protection, so you can learn about your body and cycle along the way” it is a contradiction in and of itself. If the app is doing all the work for the user, the user does not have the chance to develop any level of body literacy above a basic understanding that an ovulatory cycle should have a visibly biphasic temperature pattern. Additionally, Natural Cycles doesn’t mention crucial information about the importance of cervical fluid observations to avoiding (or gaining!) a pregnancy. In my book, this does not qualify as “getting to know your cycle.”

While I would not recommend Natural Cycles, I can also understand the relevance of the saying “A less-effective contraceptive used well, can sometimes be more effective than a highly-effective contraceptive used badly.”

For some women out there who are not inclined to use the Symptothermal Method carefully and correctly, Natural Cycles might be more effective. For some women with extremely regular cycles, Natural Cycles will probably work very well and may never present an issue. For these women, Natural Cycles can be a good gateway into discovering how Fertility Awareness works with your body. Alternatively, some women might simply like the user-interface of the Natural Cycles app, and may prefer to use it in conjunction with their existing Symptothermal Method knowledge.

However, I remain concerned about the women who will stumble across the Natural Cycles app and blindly place their trust in its predictions, without realising its potential shortcomings. If and when a percentage (however small) of these women experience an unintended pregnancy, it will more often than not reflect badly on the entire Fertility Awareness community – which is a shame considering the delicate journey to gain more mainstream awareness and use of modern FABMs.

Have you used Natural Cycles? I would love to hear your experiences (both good and bad!) below.