For the last millennia there has been an assumption that the moon must affect a woman’s menstrual cycle in some way. Or could it all be a coincidence that the lunar cycle and a woman’s cycle are about equal in length?

All prior studies done on this phenomenon were conducted on a few hundred women. For the first time ever, Glow has been able to test this hypothesis on no less than 38,205 cycles - a much more robust sample by any standard.

The conclusion: Why yes! There is indeed a relationship.

According to our analysis, which we are presenting this very day at the American Society of Reproductive Medicine (ASRM), fewer women than expected get their periods when the moon is full. Conversely, more women than expected get their periods when the moon is waxing crescent. We need to do more studies to determine the causality - but this is a step in an illuminating direction.

While Glow was running this study in conjunction with our medical advisor, Dr. Philip Chenette, for the ASRM’s annual conference, we also stumbled across another fascinating tidbit of information.

You know that oft-quoted fact that the average menstrual cycle is 28 days?

Well it turns out…not so much.

According to those 38,205 cycles we analyzed - the average menstrual period is closer to 29.9 days. (Which ties in rather neatly with the fact that the lunar cycle is about 29.5 days.)

As you can see from the chart below - lots of women assume that their cycle is 28 days and act accordingly. But knowing the true length of your cycle can greatly boost your chances of conceiving or avoiding pregnancy, depending upon your preference.

Glow is at the forefront of our emerging ability to crunch and analyze vast quantities of data. We strongly believe that with time, our conclusions will empower women to take control over their reproductive health in unexpected ways.

This is, after all, the age of data. And Glow is just getting started.