What is menstrual migraine?

Menstrual migraine is migraine that consistently occurs in a 2-day window before and the first 3 days of menstruation. It accounts for about 50 percent of attacks in women with migraine who menstruate, driven primarily by the rapid drop in estrogen in the late luteal phase.

Which cycle days are highest-risk?

The 5-day window from day -2 (two days before period start) through day +3 (third day of period) is the canonical perimenstrual high-risk window. Ovulation (cycle days 13–16) is a secondary smaller risk peak in some women.

Do hormonal contraceptives help or hurt?

It depends. Continuous monophasic combined contraceptives that flatten estrogen variation can reduce menstrual attacks for some. Cyclic regimens that include a placebo week can worsen them. This is a conversation for your doctor — Hermly does not recommend contraceptives.

Does Hermly need cycle data?

Not strictly. The model still runs without cycle data. But cycle position is one of the strongest single predictors when available — adding Apple Health cycle tracking typically lifts personal AUC by a few points.

Menstrual migraine: the hormone-cycle connection

Creator: Hermly
Published: 2026-05-16T00:00:00.000Z

Roughly half of women with migraine who menstruate notice that attacks cluster around their period. That pattern is real, well- documented, and biologically explained — primarily by the rapid drop in estrogen during the late luteal phase. This page covers the hormone-cycle mechanism, the specific cycle-day windows ICHD-3 defines, and how Hermly’s prediction model uses cycle data when you’ve granted Apple Health permission.

The estrogen-withdrawal mechanism

In a typical 28-day cycle, estrogen peaks twice — around ovulation (day 13–14) and mid-luteal (day 21). It then drops sharply in the 2–3 days before menstruation begins. That drop is the trigger event for menstrual migraine. Several converging lines of evidence support this:

Stable-estrogen regimens (continuous monophasic combined contraceptives) reduce menstrual attacks in many women, because they flatten the drop.
Estrogen-priming studies in lab settings reproduce the characteristic 24–48-hour delay between drop and headache.
Migraine pattern in pregnancy — frequency typically falls sharply in the second trimester (high stable estrogen) and may spike postpartum (rapid estrogen withdrawal).

The mechanism likely involves multiple downstream effects of estrogen withdrawal — changes in cortical excitability, CGRP release, and serotonergic tone — rather than a single pathway.

The high-risk windows

ICHD-3 defines pure menstrual migraine as attacks occurring exclusively in the 5-day window from day -2 through day +3 of menstruation, in at least two of three consecutive cycles. The more common pattern is menstrually-related migraine — attacks in that window plus attacks at other times of the cycle.

Hermly’s rule engine treats two cycle windows as high-risk:

Perimenstrual (days 25–28 of cycle + days 1–2 of period) — the canonical estrogen-withdrawal window. Receives the larger weight.
Ovulatory (days 13–16) — a smaller secondary peak in some women, associated with the briefer estrogen swing around ovulation.

These windows are derived against a reference 28-day cycle. Actual cycle lengths vary — Hermly reads your Apple Health cycle data to align the windows to your personal length.

Why cycle data improves the model

Among the 26 features Hermly reads, cycle phase is one of the stronger single predictors for women whose attacks have a hormonal component. The published HAPRED line and the Lateef 2024 EMA study both treat cycle data as a top-tier feature when available.

When cycle data isn’t available — you haven’t logged a period in Apple Health, or cycle tracking is off in Settings — the model falls back on the other 25 features. The prediction is still useful; it’s just missing one signal. The Today screen renders the cycle factor card as a quiet ”—” rather than a fabricated reading.

There’s also active research on inferring cycle phase from wrist-temperature anomaly + HRV alone (npj Women’s Health 2025), reaching ~96 percent accuracy classifying menstrual / ovulatory / luteal phases. Hermly does not yet wire this in — Apple Health cycle data is the authoritative source — but the option exists as a fallback for users who don’t track cycles manually.

Hormonal contraceptives — beyond Hermly’s scope

The interaction between menstrual migraine and hormonal contraception is a real medical conversation, and not one Hermly participates in.

Combined hormonal contraceptives are sometimes effective for menstrual migraine but carry a small stroke risk specifically in women who experience migraine with aura — a contraindication the WHO classifies as a category 4 risk.
Progestin-only methods are typically considered safer when migraine with aura is present.
Continuous (no-placebo) regimens can flatten the estrogen drop and reduce attacks.

These trade-offs are individual. Talk to your doctor; Hermly will never recommend a contraceptive.

What this page is not

Not a substitute for an evaluation. If menstrual attacks are debilitating, the conversation to have is with a gynaecologist or neurologist with experience in hormonal headache. Preventive options specific to menstrual migraine include short-term triptans, NSAIDs, or estrogen-stabilising regimens — all out of scope for what an app can responsibly recommend.

What Hermly does is make the cycle-attack correlation legible — through the cycle factor card, the doctor report, and the next-day risk number that takes cycle phase into account.

Not medical advice. Hermly is a wellness app, not FDA-cleared for diagnosis or treatment. This page is informational and should not replace conversation with your doctor. If you're experiencing a sudden, severe, or unusual headache, contact a medical professional or emergency services.