How do periods normally change in perimenopause?
The transition unfolds in a recognizable sequence, mapped by a staging system called STRAW+10 — the Stages of Reproductive Aging Workshop, updated in 2012.11
In the late reproductive stage, cycles are still mostly regular. You might notice subtle changes — a day shorter here, a bit heavier there — but nothing obviously different.
In early menopause transition, you reach a threshold that STRAW+10 defines as a persistent difference of seven or more days between consecutive cycle lengths.11 In plain terms: if one cycle is 28 days and the next is 36, that counts. This variability is one of the earliest clinical markers that the transition has begun.
In late menopause transition, at least one gap of 60 days or more occurs between periods.11 Cycles are now coming and going unpredictably.
The final menstrual period (FMP) can only be identified in hindsight — after 12 full months of no periods, the last period you had gets labeled the FMP.11 The first five to eight years after that date is early postmenopause.
None of this is illness. It is an arc.
Why do cycles get irregular in the first place?
The short answer: your ovaries are ovulating less reliably, and that changes everything downstream.
In the late 40s, the supply of egg-containing follicles is declining. When a follicle doesn't develop fully, ovulation doesn't happen — a cycle called an anovulatory cycle (anovulation simply means "no egg released that month"). That's important because ovulation is what triggers progesterone production in the second half of your cycle.
Without that progesterone signal, the uterine lining grows under estrogen alone, then sheds when it can no longer sustain itself. The result: cycles that are shorter or longer than usual, periods that are heavier or lighter than expected, or a stretch of nothing followed by a sudden bleed. Anovulatory cycles are extremely common in perimenopause and explain the majority of "my periods have gone weird" complaints — but they can occasionally become problematic if heavy or prolonged bleeding leads to anemia.
What does the PALM-COEIN framework mean for you?
When bleeding goes beyond the expected weirdness of anovulation, clinicians use a classification system called PALM-COEIN — developed by the International Federation of Gynecology and Obstetrics (FIGO) and endorsed by the American College of Obstetricians and Gynecologists (ACOG) — to organize the possible causes.2233
The name is an acronym for two groups of causes:
PALM — structural causes your doctor can usually see on ultrasound or biopsy:
- Polyp (a small growth on the uterine lining)
- Adenomyosis (when the lining tissue grows into the uterine muscle itself)
- Leiomyoma (the medical term for fibroids)
- Malignancy and hyperplasia (cancer or pre-cancerous overgrowth of the uterine lining)
COEIN — non-structural causes:
- Coagulopathy (a blood-clotting disorder)
- Ovulatory dysfunction (anovulation, as described above)
- Endometrial (a problem with the lining itself, not a structural growth)
- Iatrogenic (caused by a medication or device)
- Not otherwise classified
What bleeding patterns are red flags?
Most cycle changes in perimenopause fall inside the expected range. These specific patterns do not:
- Soaking a pad or tampon every hour for two or more hours in a row. This is heavy menstrual bleeding by clinical definition, and it can lead to iron-deficiency anemia.
- Periods lasting more than seven days.
- Periods coming more often than every 21 days.
- Any bleeding between periods — spotting that starts and stops outside of your expected window.
- Bleeding after sex (called post-coital bleeding). This is always worth investigating; it can signal a cervical or uterine issue.
- Any bleeding after 12 months of no periods. This is postmenopausal bleeding, and it is never a normal part of perimenopause.
- Symptoms of anemia: unusual fatigue, shortness of breath on exertion, heart palpitations, or an unusual craving for ice or dirt (called pica). These suggest that blood loss has been heavy enough to lower your iron stores.
What does a workup actually involve?
If you bring any of the above concerns to your clinician, a standard evaluation might include:4455
- Pregnancy test, if there is any possibility of pregnancy.
- TSH (thyroid-stimulating hormone) — because thyroid problems are a common, easily missed cause of irregular bleeding.
- CBC (complete blood count) and ferritin — to check for anemia and iron stores, especially if your periods have been heavy.
- Transvaginal ultrasound — to look at the uterus and ovaries and measure the thickness of the uterine lining.
- Endometrial biopsy — a quick in-office procedure to sample the uterine lining and check for abnormal cells.
- Saline-infusion sonohysterography or hysteroscopy — if the initial imaging suggests a polyp or fibroid inside the uterine cavity, these allow a clearer look.
Treatment depends entirely on what the workup finds. For heavy bleeding without a structural cause, options include tranexamic acid (a medication that slows bleeding during periods), a levonorgestrel-releasing IUD (which dramatically reduces period volume over time), combined hormonal contraception, or cyclical progestogens to regulate the lining.55 Structural problems like fibroids or polyps may be managed medically or surgically, depending on their size and location.
What's actually worth tracking before your appointment?
A simple period log — even just notes in a phone app — gives your clinician far more to work with than memory alone. Useful things to record:
- The first day of each period.
- How many days it lasted.
- Flow heaviness (lightest to heaviest, or pad/tampon count per day).
- Any spotting or bleeding outside of your normal window.
- Any bleeding after sex.
Even two or three months of data can make the pattern clear and shorten the workup.