Can we rely on fertility apps to predict the fertility window?

Updated: Dec 22, 2020

Smartphones have become a fundamental part of our lives. It's very difficult to imagine our daily routine without all those apps that fulfil our every need.

These apps not only help us keep track of our social events, our to-do lists, but also our very own body - be it fitness or health. All iPhones have the in-built Health app that allows you to store a huge array of health data and sort through it with ease. Blood glucose, weight, heart rate, even hearing and period health are all right there at your fingertips 24/7.

Applications like the iOS Health app are really amazing for tracking our daily physical activity and keeping an eye on our heart rate, but can we rely on those apps to track and evaluate more complex parameters like blood sugar levels, mental health status and fertility window?

In today's article, we will discuss the Fertility app hype. These apps supposedly track our menstrual cycle and predict our so-called "fertility window", a period of time when a woman has a high chance of getting pregnant.

But before we get to the more controversial part, we need to understand the menstrual cycle.

Menstrual cycle

Hormones are small chemicals released from different glands spread across different parts of our bodies. It is fascinating how these tiny chemicals control an unimaginable amount of activities in the organism. Hormones control our mood, weight, sex drive, intelligence, the condition of our skin and so on and on and on. It therefore shouldn't come as a surprise that also the female reproductive tract is heavily influenced by hormones - more specifically the reproductive hormones.

These reproductive hormones infamously fluctuate during the menstrual cycle. These fluctuations have a direct effect on the female reproductive tract. They change the uterine tissue to provide the most favourable conditions for reproductive success.

The physiology of the menstrual cycle is a very complicated topic (it took us hours and hours to understand it for our bachelor exams), therefore, we will explain it in very simple and easy to understand terms. If, however, you want more information about it we will suggest some links to excellent scientific papers.

The orchestra of reproductive hormones that control the menstrual cycle are released from three sources: two glands found in the brain (the pituitary gland and the hypothalamus) and the ovaries. The menstrual cycle consists of three phases:

1) The follicular phase

2) The ovulatory phase

3) The luteal phase

(Remember the number 3: three sources and three phases)

David Meerman Scott, the author of "The New Rules of Marketing & PR", highlights the importance of infographics for visualisation of complex concepts. Therefore, we decided to summarise key information about the menstrual cycle in a nice infographics presented below. Please let us know in the comments below if you found it easy to understand the "nitty-gritty" of the menstrual cycle from our chart.

Fertility apps

To date, there are just over 200 fertility tracking apps (FTAs) available on iOS App store and Google Play. These apps are classified as mobile health apps. Roshonara Ali, a final year medicine student and a MSc in Women’s Health at University College London graduate, investigated the reliability of fertility apps and made some interesting observations you'll want to know.

Just over a half of the apps that met her inclusion criteria based the fertility window predictions by solely tracking menstrual cycle dates, which is not the most reliable method as ovulation dates fluctuate even for women with regular cycles. The rest of the apps included at least one additional fertility-awareness method like basal body temperature, LH levels (a reproductive hormone) and cervical mucus. Only 27.8% of studied apps used all three methods.

One of the most remarkable findings of the study - in our opinion - was that free to download apps had "more desirable features, tracked more measures and had more and better quality educational insights than paid apps". This only goes to show that expensive does not necessarily mean better.

One of the main conclusions of her cross-sectional study was:

"It is impossible to predict the day a woman ovulates by simply looking at her menstrual cycle dates...It is alarming that calendar apps were found to be the most commonly available...These apps are giving women inaccurate information about their fertile window. Those trying to conceive using these apps may waste precious time if a couple have intercourse at the wrong time, and for those trying to avoid pregnancy they may conceive as they are avoiding intercourse on the wrong days"

Therefore the bottom line is that most of the fertility apps are really not a reliable source for predicting the fertility window.

We hope that you found our post interesting and helpful!

Lots of love,

Karima and Danielle


Ali, R., Gürtin, Z.B. and Harper, J.C., 2020. Do fertility tracking applications offer women useful information about their fertile window?. Reproductive BioMedicine Online.

Bull, J.R., Rowland, S.P., Scherwitzl, E.B., Scherwitzl, R., Danielsson, K.G. and Harper, J., 2019. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. NPJ digital medicine, 2(1), pp.1-8.

Wang, W., Vilella, F., Alama, P., Moreno, I., Mignardi, M., Isakova, A., Pan, W., Simon, C. and Quake, S.R., 2020. Single-cell transcriptomic atlas of the human endometrium during the menstrual cycle. Nature Medicine, 26(10), pp.1644-1653.

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