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Menstrual cycle phase more varied than previously thought – study

By Published On: October 8, 2024
Menstrual cycle phase more varied than previously thought – study

The menstrual cycle’s luteal phase – the time from the egg being released until the next flow – may be more varied than previously thought, according to a new study.

The current expectation is that every ovulatory menstrual cycle will have a luteal phase that lasts approximately 14 days, with ovulation covering half of the expected 28-day menstrual cycle.
But new findings published in the journal Human Reproduction show that the luteal phase is quite variable, with a normal luteal phase length found to be more than or equal to 10 days; and a short cycle less that 10 days.
Researchers studied 53 healthy women’s cycles over a year; all had at least eight, and an average of 13 menstrual cycles. Using a validated technique called the quantitative basal temperature method it was found that only six of 53 women (11 per cent) had normally ovulatory cycles during the year, while 55 per cent had more than one short luteal phase in an ovulatory cycle.
First author Sarah Henry of the University of British Columbia said: “We discovered a wide variety of luteal phase lengths, even in healthy premenopausal women who needed two cycles in a row that were both of normal cycle length and ovulatory in order to join the original study.

“Although the luteal phase was not predictable in length, it was usually less variable than the follicular phase.”

The researchers cite a paper published in 2014 (Li D, Epidemiol Rev) which shows bone loss in women with more short luteal phase ovulatory and anovulatory cycles compared with those having more normally ovulatory cycles over a year, even if all cycles remained month-apart.

It is also likely that short luteal phase cycles, as well as those without ovulation, are related to trouble becoming pregnant.

Senior author Jerilynn Prior said: “It is important to know about our own ovulation and luteal phase lengths. Why? Because increasing evidence says that estrogen, a powerful growth stimulator, needs to be counterbalanced.

“Progesterone decreases proliferation while encouraging cells to become more well-developed and specialised.”

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