Our Clinical Study
Ava completed a year-long clinical study at the University Hospital of Zurich under the lead of Prof. Dr. Brigitte Leeners, a leading expert on the mathematical modeling of menstrual cycles. Ava was found to identify an average of 5.3 fertile days per cycle with an accuracy of 89 percent.
The clinical study used a wearable device to track nine physiological parameters throughout 155 menstrual cycles. The data gathered was cross referenced with urine tests taken during the fertile phase.
The results of the study were presented in June 2016 at the Swiss Society of Obstetrics and Gynecology Annual Congress and in October at the German Society of Obstetrics and Gynecology Annual Congress. Bayer, the leading women’s health company, is sponsoring Ava’s presentation.
Our scientific research paper will be submitted in summer 2016. We expect it to be published by a leading peer-reviewed journal in reproductive health by the end of 2016.
Ava is planning further clinical studies to refine its algorithms for use in both pregnancy recognition, pregnancy monitoring, and possible use as a non-hormonal contraceptive device.
How physiological parameters can be used to identify fertile days.
There are only a few days per cycle when it is possible for a women to conceive. These days vary from woman to woman and from cycle to cycle, but studies show that this time usually lasts six days, beginning five days prior to ovulation and lasting until the day of ovulation itself.
Not all women experience six fertile days. The fertile window is impacted by:
- The lifespan of the egg, which is up to 24 hours after ovulation
- The lifespan of the sperm. The median is 1.5 days, but when fertile-quality cervical mucus is present, some high-quality sperm can survive up to five days.
The fertile window begins with a gradual rise in estradiol levels over three days9, along with a moderate probability for conception. The two days that follow are characterized by high levels of estradiol in combination with a surge in luteinizing hormone. These two days, along with the day of ovulation, represent peak fertility, with a pregnancy probability of more than 20 percent. Seventy percent of pregnancies are conceived in these latter three days of the fertile window.
After ovulation, the likelihood of conceiving drops rapidly due to the limited lifespan of the follicle (typically 12-24 hours).10
Tracking physiological parameters associated with the rise in estradiol allows women to recognize the first days of the cycle when conception is possible, and provides advance warning of peak fertile days. Research shows that women who track their fertile days are twice as likely to conceive in a given month (compared with untimed intercourse once per week). 11
The rise in estradiol levels stimulates the secretion of fertile quality cervical mucus, which supports the survival and transport of sperm. Intercourse that occurs after estradiol levels rise may lead to conception, as some sperm can survive for several days in favorable environments.
Changes in reproductive hormone levels have measurable physiological impacts throughout the body. 12 For example, it has been understood for decades that progesterone has a direct impact on basal body temperature 13, causing a BBT spike by one half to one degree Fahrenheit after ovulation. Charting temperature with a BBT thermometer has been shown to be a moderately effective method for detecting when ovulation has occurred.
Advancements in sensor technology make it possible to collect physiological data points continuously over long periods of time, enabling more precise monitoring of correlations between the hormones progesterone and estradiol with physiological parameters. The Ava fertility tracker is the first fertility tracking device to collect data continuously throughout the night, allowing it to detect an average of 5.3 fertile days per cycle with minimal user effort.
- Schafer, A., & Vagedes, J. (2013). How accurate is pulse rate variability as an estimate of heart rate variability? A review on studies comparing photoplethysmographic technology with an electrocardiogram. International Journal of Cardiology, 166(1): 15–29. ↩
- Kräuchi, K., Konieczka, K., Roescheisen-Weich, C., et al. (2014). Diurnal and menstrual cycles in body temperature are regulated differently: A 28-day ambulatory study in healthy women with thermal discomfort of cold extremities and controls. Chronobiology International, 31(1): 102–113. ↩
- Cerutti, S., Bianchi, A. M., & Reiter, H. (2006). Analysis of sleep and stress profiles from biomedical signal processing in wearable devices. Annual International Conference of the IEEE Engineering in Medicine and Biology – Proceedings, 6530–6532. ↩
- De Zambotti, M., Nicholas, C. L., Colrain, I. M., et al. (2013). Autonomic regulation across phases of the menstrual cycle and sleep stages in women with premenstrual syndrome and healthy controls. Psychoneuroendocrinology, 38(11), 2618–2627. ↩
- Nunan, D., Sandercock, G. R. H., & Brodie, D. A. (2010). A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. PACE – Pacing and Clinical Electrophysiology, 33(11): 1407–1417. ↩
- Carskadon, M. A., & Dement, W. C. (2011). Normal Human Sleep : An Overview. Principles and Practice of Sleep Medicine,5:16–26. ↩
- Mercuro, G., Pitzalis, L., Podda, A., et al. (1999). Effects of Acute Administration of Natural Progesterone on Peripheral Postmenopausal Women. American Journal of Cardiology, 84, 214–218. ↩
- Gerhardt, U., Hillebrand, U., Mehrens, T., & Hohage, H. (2000). Impact of estradiol blood concentrations on skin capillary Laser Doppler flow in premenopausal women. International Journal of Cardiology, 75(1), 59–64. ↩
- Fritz 2012 ↩
- Wilcox 1996 ↩
- Wilcox AJ, Weinberg CR, Baird DD. Timing of Sexual Intercourse in Relation to Ovulation. Obstet Gynecol Surv. 1996;51(6):357-358. doi:10.1097/00006254-199606000-00016. ↩
- Hirshoren N, Tzoran I, Makrienko I, et al. Menstrual cycle effects on the neurohumoral and autonomic nervous systems regulating the cardiovascular system. J Clin Endocrinol Metab. 2002;87(4):1569-1575. doi:10.1210/jc.87.4.1569. ↩
- Kräuchi K, Konieczka K, Roescheisen-Weich C, et al. Diurnal and menstrual cycles in body temperature are regulated differently: A 28-day ambulatory study in healthy women with thermal discomfort of cold extremities and controls. Chronobiol Int. 2014;31(1):102-113. doi:10.3109/07420528.2013.829482. ↩