The Menstrual Cycle Gets a Makeover

In the 1950s, using data from the American population which was much less ethnic diverse than now, studies of a typical menstrual cycle were undertaken.

In this month’s Obstetrics and Gynecology a new study updating the data was released.

Smart phone menstrual cycle data from over 300,000 women in Japan was studied to see if there are any new trends in the world of climate change, stress, and women in the work force.

In fact the seasons do both relate to and change your menstrual cycles and a women’s basal body temp! A never before recognized fact!

Generally body temp during the cycle will only vary a degree or two. And stability of your temperature day to day is an index of healthy aging and longevity long after cycles stop.

Looking at the population, mean length of cycles increases from 15-23, then decrease until age 45, and lengthens out again

Women with PCOS actual have some trend towards normalization of their cycles in their mid to late 30s, and thus looking at a whole makes cycle lengths look like they shorten for all of us at that time.

The longest population average length of the menstrual cycle peaks around age 23. This corresponds perfectly with the peak of fertility which is age 22-23. In addition you are least likely to have a miscarriage at age 23.

Temperature trends in the menstrual cycle are cumbersome and have enough error that the ASRM recommends not bothering with BBTs when you are trying for pregnancy.

Basal temperatures are warmest during the warmest months, as we would think.

Remember, if you are trying to get pregnant, transitioning to menopause, or finding your cycles have changed, come in and have a visit with us at Women’s Health Practice first and discuss all aspects of your health, not just your menstrual cycle!


Suzanne Trupin, MD, Board Certified Obstetrician and Gynecologist and owner of Women's Health Practice, Hada Cosmetic Medicine, and Hatha Yoga and Fitness

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