I would like to preface this article by saying that there is no need to panic if you are a current Daysy user. Instead, this would be a good time to do a little research and re-evaluate whether you are still happy to continue using the device based on how seriously you are wanting to avoid an unplanned pregnancy. Considering we don’t see thousands of women complaining of unintended pregnancy, it is clear that the Daysy device has some level of effectiveness; however, what that effectiveness actually is remains unknown at this point in time.

This week, the study behind Valley Electronics’ claims of a 99.4% effective Daysy device has finally been retracted from the Journal of Reproductive Health. This follows a peer-reviewed scientific commentary by leading reproductive health researcher Dr Chelsea Polis which was published back in June 2018. Dr Polis’ commentary called for the Daysy study to be retracted due to grave methodological flaws which were inflating consumer confidence and potentially putting users at risk of unintended pregnancy. You can read more about the retraction in this Buzzfeed article and more from Dr Polis on her personal blog.

Unfortunately, Valley Electronics (the manufacturer of Daysy) had been aware of Dr Polis’ concerns since 2017 and had made no move to alert their users or amend any of their marketing materials. Following the publication of Dr Polis’ peer-reviewed commentary in June 2018, Daysy again made no further move to alert their customers or amend any of their marketing materials. In fact, their marketing materials have continued to reference a 99.4% effectiveness rating ever since – despite the fact that their study was under investigation to be retracted.

The original peer-reviewed commentary by Dr Polis referenced a number of issues that may have affected the accuracy of the findings of the Daysy study:

1. Users with less than 13 cycles’ use of the Daysy were excluded from the calculations. Within this group of excluded data were 10 pregnancies. We don’t know how this might have affected the effectiveness rates.
2. The survey behind the study only had a 13% response rate. This raised questions about selection bias – would those who had a bad experience with the Daysy device still be in conctact with the company, and if so would they want to participate in such a survey?
3. Daysy relied on users to self-report an unintended pregnancy – they didn’t objectively look at all the data to detect a pregnancy based on extended elevated temperatures.
4. The wording of the survey itself was slightly ambiguous and may have resulted in confusion.
5. The survey didn’t gather information to exclude users that were subfertile (i.e. post-hormonal birth control, postpartum or perimenopausal.

Importantly, Dr Polis’ has emphasised that many of these issues also apply to Daysy’s older studies which used to reference a 99.3% effectiveness rate. Because of this, the true effectiveness of the Daysy device currently remains unknown.

I don’t personally use or recommend temperature-only devices and apps such as Daysy or Natural Cycles, and you can read about why here: 5 Reasons I Don’t Use Daysy Or Natural Cycles. 

Essentially though, the main reason is that basal body temperature is not a predictive fertility biomarker – it only rises after ovulation has already occurred. Because sperm can survive up to 5-7 days in the reproductive tract in ideal conditions, we need to have advance warning that ovulation is approaching. Basal body temperature cannot provide this advance warning, as it only rises after ovulation has already occured. This means that Daysy and Natural Cycles are making educated guesses about when you might be fertile in your current cycle, based on data from your past cycles and other users. This is problematic because there are many external factors that can cause you to ovulate earlier or later than expected (such as stress, illness, travel, supplements, diet and lifestyle changes).

I recommend the Symptothermal Method of Fertility Awareness instead, which tracks both cervical fluid and basal body temperature. Cervical fluid is influenced by oestrogen levels, which rise in the lead-up to ovulation. In this way, cervical fluid can provide advance warning of ovulation, whereas basal body temperature cannot. If you are interested in learning the Symptothermal Method I recommend working with an instructor and you can find one here.

If you’re seriously needing to avoid pregnancy, it’s important to work with an instructor of the Symptothermal Double-Check Method. Why? Because as it stands, no studies have investigated the effectiveness of self-teaching the Symptothermal Method: the effectiveness of self-teaching currently remains unknown.

If you’re a big fan of femtech in your day-to-day life, there’s no need to resort to charting your cycles on paper if that’s not a good fit with your lifestyle. There are a number of free apps such as Kindara that you can use to record your charting observations, and the Tempdrop is a great option if you’re after a wearable thermometer that takes your temperature throughout the night. The key here is that this femtech is used to collect and chart your information – interpretation of that information remains up to you, the user.

Anecdotally, if you are absolutely certain that you wish to use either Natural Cycles or Daysy, it appears that Daysy has a much safer algorithm than Natural Cycles. The amount of unintended pregnancies and scares that I see with Natural Cycles users is truly concerning. If you are seriously trying to avoid pregnancy please steer very clear.

Ultimately, I believe both options are simply glorified and expensive thermometers dressed up in high-tech disguise; however, they can be useful tools for those who have no desire to learn to chart their cervical mucus – as long as those users are fully informed of the accurate effectiveness rates. In saying this, the real benefits of Fertility Awareness-Based Methods lie in the body literacy they provide – and Daysy and Natural Cycles come nowhere close.

Have you used the Daysy device or the Natural Cycles app? I would love to hear your experience in the comments below.