Global study confirms ovulation often continues into perimenopause

Natural Cycles, the first FDA-cleared digital contraceptive app, has released findings from the largest study ever conducted on menstrual and ovulatory patterns — uncovering new biological insights into what happens to ovulation during perimenopause.

In collaboration with research experts from George Washington University, Seattle Clinical Research Center, Gennev, and UC San Diego, the study analyzed nearly one million menstrual cycles from more than 197,000 women aged 18–52 across 140+ countries — a scale never before possible in women’s health research.

Findings

This extensive dataset enabled researchers to examine menstrual patterns in far greater detail, including across various age ranges, distribution, and whether ovulation occurred in those cycles. This analysis yielded several key findings. 

One of the most significant findings came from analyzing cycle length by age group. The study showed that the average cycle length tends to get longer starting in the mid-40s, as might be expected since this is when some women start to notice their periods coming further apart (commonly referred to as “skipped periods”). However, longer cycles are not the only cycle change experienced by women in their 40s and early 50s. In fact, some women can experience very short cycles. This trend could easily be overlooked unless we look at the broader distribution of cycle length — that is, how cycle lengths vary across menstrual cycles.

Another key discovery emerged from analyzing cycles that are medically considered atypical, specifically those that are fewer than 21 days in length. Historically, such short cycles have been associated with anovulation, when ovulation doesn’t occur. The data tells a different story: while anovulation is typical for women in their early 20s with shorter cycles, ovulation still happens in the vast majority of very short cycles in women in their 40s and early 50s.

This highlights a shift in our understanding of ovulation in the later reproductive years. Even though cycles get shorter and the onset of menopause approaches, the presence of ovulation means there is still a chance of conception, and therefore contraception and/or ovulation tracking should be a key consideration at this phase of life. 

Summary

The scale of the Natural Cycles dataset allowed for a level of analysis that had never been previously carried out. From the breadth of this research, several new insights emerged, including the learning that although menstrual cycles become longer on average as menopause approaches, very short cycles are also common during this time. In addition, the findings showed that these shorter cycles typically included the release of an egg cell, contrary to the common belief that these cycles are a sign that ovulation might be disturbed and not happen that cycle.

The full study will be published in the December 2025 issue of the journal Menopause.