For the past ten years, digital technology companies dedicated to women’s health (sometimes termed ‘FemTech’) have been booming. A key sector is that of smartphone apps that follow menstrual cycles and predict users’ fertility periods for the purposes of contraception or conception. Several hundred million women around the world use them in their daily lives.

Recent research has examined the methodologies used by apps for menstrual tracking^1,2. The majority of them use the period calendar to predict the fertile interval and ovulation date. This finding is alarming because this method, which is based on the date of ovulation occurring 14 days after the beginning of menstruation, is widely recognized as unreliable³. This suggests that app predictions may be misleading. Even women with very regular menstrual cycles have variable ovulation days. Variations in cycle length of seven days or more affect half of the female population, which casts doubt on the predictive capabilities of these apps^4,5.

在过去的十年里，致力于女性健康的数字技术公司（有时称为“FemTech”）一直在蓬勃发展。一个关键领域是智能手机应用程序，它跟踪月经周期并预测用户的生育期，以便避孕或受孕。全世界有数亿女性在日常生活中使用它们。

最近的研究检查了应用程序用于月经跟踪的方法^1,2。他们中的大多数人使用经期日历来预测受孕间隔和排卵日期。这一发现令人震惊，因为这种方法基于月经开始后 14 天的排卵日期，被广泛认为是不可靠的³。这表明应用预测可能具有误导性。即使是月经周期非常规律的女性，排卵天数也存在差异。7 天或更长时间的周期长度变化会影响一半的女性人口，这让人对这些应用程序的预测能力产生怀疑^4,5。