Tracking your cycle with PCOS (now called PMOS)

A straight account of what tracking can tell you with PMOS, what it can’t, and how Bloom handles long, unpredictable cycles.

Last reviewed 7 October 2026Checked against the sources listed below

If you have PCOS, or think you might, a period tracker can be genuinely useful: it turns “my periods are all over the place” into dates and patterns you can show a doctor. But many apps promise more than a tracker can deliver, especially about ovulation. This page is a straight account of both sides, and of how Bloom handles long and unpredictable cycles.

PCOS has a new name: PMOS

In 2026 the condition long known as polycystic ovary syndrome was renamed polyendocrine metabolic ovarian syndrome, or PMOS. The NHS now uses the new name and notes that PMOS used to be called PCOS.^[1] The old name suggested the condition was about cysts on the ovaries; the new one reflects that it involves hormones and metabolism across the body. You will see both names for a while, and they mean the same condition.

What PMOS can do to your cycle

The NHS lists irregular periods, or long gaps between periods, among the main symptoms of PMOS. Others include extra hair growth or hair loss, weight gain, oily skin and acne, difficulty getting pregnant, feeling very tired, and mental health problems such as depression or anxiety.^[1] Symptoms can be mild or severe, and some people have none.

The key thing for tracking is ovulation. Irregular cycles can be ovulatory, meaning an egg is released, or anovulatory, meaning it is not.^[2] With PMOS, ovulation may happen late, unpredictably, or not at all in a given cycle, which is why periods become hard to predict.

What a period tracker can and can’t tell you

Why app ovulation dates are shaky with PMOS

Most apps estimate ovulation from the calendar: they assume it happens roughly two weeks before your next period and count back from the predicted date. Bloom starts the same way. If you log ovulation tests or cervical fluid, it uses those signs to adjust its estimate, and after a couple of cycles with them it works from your own timing instead of the textbook two weeks. Even in regular cycles, the day of ovulation moves around — in a large analysis of app data, the first half of the cycle ranged from about 10 to 30 days.^[3] When cycles are irregular, or when ovulation doesn’t happen, a calendar estimate can be far off.

So treat any app’s “ovulation” or “fertile” days with care if you have PMOS. In Bloom the ovulation phase is an estimate to help you understand your cycle, nothing more: a sign you log is a clue, and Bloom can’t confirm that ovulation actually happened. Bloom is not a method of contraception and is not a fertility tool, and it should not be used to avoid or plan a pregnancy. If you are trying to conceive, a doctor can talk you through tests that actually check ovulation.

How Bloom handles long cycles

Many trackers quietly discard very long cycles as mistakes. Bloom deliberately doesn’t:

• Cycles up to 90 days count. Any gap between periods from 15 to 90 days is treated as a real cycle, so your longest cycles stay in your record instead of being dropped.
• Predictions follow your recent pattern. Bloom uses the median of your last six cycles, so one unusual month doesn’t wreck the next prediction, and a change in your body shows up within a few cycles.
• “Late” is judged against your own spread. If your cycles naturally swing by a week or two, Bloom learns that and doesn’t call you late every month.
• No fake new cycles. When a period hasn’t come, Bloom waits and says so, instead of pretending a new cycle began on schedule.

You can also tell Bloom during setup that you have PCOS. Bloom AI takes that into account when it answers you, but it does not change how dates are predicted: your logged dates do that.

What to track before an appointment

If you are seeing a doctor about irregular periods or possible PMOS, a few months of notes make the conversation much easier:

• The first day of each period, and how many days you bled.
• How long each cycle was, and the longest gap between periods.
• Symptoms you noticed and when: acne, tiredness, cravings, low mood or anxiety.
• Anything that changed: a new medication, illness, stress, travel or poor sleep.
• Things Bloom doesn’t record, such as changes in your weight or hair, which are worth writing down separately.

Bloom keeps your period dates, symptoms and notes together on your phone, so you can scroll back through them with your doctor. For more on unpredictable cycles in general, see a period tracker for irregular periods.

Bloom is a wellness and planning app. It is not a medical device, it does not diagnose or treat any condition, and it is not a method of contraception. This page is general information, not medical advice. If something about your cycle worries you, talk to a doctor, nurse or midwife.