PeriWise
In short
- Changing cycle length is often the first measurable sign of perimenopause — commonly shortening before it lengthens.
- Irregular does not mean infertile: contraception remains a real consideration until menopause is confirmed.
- Some bleeding changes are not 'just perimenopause' and warrant a medical check — very heavy, very prolonged, or any bleeding after 12 period-free months.
- Tracking dates turns chaos into information: the pattern of irregularity is itself diagnostic.
For thirty years your cycle may have been the one reliable calendar in your life. Then it starts freelancing: 24 days, then 31, then a skipped month, then two arrive close together. This is often the earliest measurable signature of perimenopause — and paradoxically, the chaos has structure.
Why cycles change
As the ovarian follicle supply declines, ovulation becomes inconsistent. Cycles without ovulation, or with weaker hormonal signals, shift in length — commonly shortening in early perimenopause, then lengthening and skipping as the transition progresses. Flow changes too: estrogen-progesterone imbalance can make some periods unexpectedly heavy and others barely there.
What the pattern can tell you
Clinical staging of the transition (the STRAW+10 framework researchers use) is built largely on cycle patterns: persistent differences of seven or more days between consecutive cycles mark the early transition; gaps of sixty days or more mark the late transition, when the final period is statistically approaching. Your dates, written down, are genuinely diagnostic data — which is why every doctor will ask, and why guessing from memory undersells you.
The part nobody mentions: contraception
Irregular ovulation is not absent ovulation. Pregnancy in perimenopause is uncommon but entirely possible, and guidance is to use contraception until menopause is confirmed — twelve months without a period (age-dependent; discuss specifics with your clinician). And to be explicit about our own lane: PeriWise's cycle view estimates from your logged history for orientation only. Perimenopausal cycles are inherently unpredictable — never use any app's estimate for contraception or to plan a pregnancy.
Changes that deserve a doctor's look
- Bleeding heavy enough to soak through protection hourly, or lasting well beyond a week
- Bleeding between periods or after sex
- Any bleeding after twelve consecutive period-free months
- Cycle chaos with severe pain, or alongside symptoms like unexplained weight loss
Most of these have benign explanations — fibroids and polyps are common in the 40s — but they are check-now items, not wait-and-see items.
Our takeaway
Log the dates, even the weird ones — especially the weird ones. Irregularity you can show is information; irregularity you half-remember is anxiety.
Frequently asked questions
Are irregular periods always perimenopause after 40?
Often, but not automatically — thyroid conditions, fibroids, polyps and other causes can change bleeding patterns too. A doctor can distinguish them, and your logged dates make that much easier.
Can I still get pregnant with irregular perimenopausal cycles?
Yes. Ovulation still happens unpredictably. Contraception is generally advised until menopause is confirmed — discuss the right approach and timeline with your clinician.
What bleeding changes should I see a doctor about?
Very heavy or prolonged bleeding, bleeding between periods or after sex, and any bleeding at all after 12 consecutive months without a period.
See your own pattern
PeriWise is a private iOS app for tracking perimenopause symptoms — logging is free, your data never leaves your iPhone, and doctor-ready PDF reports are always included. Get the app or browse Things That Helped.
Sources
Everything above is our own writing. The facts come from these sources — always read the originals:
- Harlow SD et al. — Executive summary of STRAW+10: addressing the unfinished agenda of staging reproductive aging (PMC) — https://pmc.ncbi.nlm.nih.gov/articles/PMC3340903/
- NICE NG23 — Menopause: identification and management — https://www.nice.org.uk/guidance/ng23
- The Menopause Society — patient resources on the transition — https://menopause.org/