Possible Anovulation Cycle Flag™ explained
You can bleed on schedule and still not have ovulated. It’s called an anovulatory cycle, and awareness of whether and when this occurs can be an important window into your health.
Cycle Flags add context to your cycle on the Ultrahuman Ring. Which flags you see depends on your plan and region. A flag is a gentle heads-up about a pattern, not a diagnosis.
In this guide, we explain what an anovulatory cycle is, how the Ultrahuman Ring detects it, and when a pattern is worth discussing with your doctor.
- The Ultrahuman Ring raises a Possible Anovulation Cycle Flag when the overnight temperature rise that normally follows ovulation doesn't appear.
- A cycle can bleed on schedule but not have released an egg.
- Anovulation is often temporary. Illness, travel, hard training, and long stretches of undereating can all cause a skipped cycle.
- But anovulation can also be present in women with an ovulatory disorder like polyendocrine metabolic ovarian syndrome (PMOS, until recently called PCOS) or a thyroid condition.
- In Ultrahuman's cycle research, the Possible Anovulation flag tracked with self-reported irregular cycles more strongly than any other flag.
What happens in an anovulatory cycle
In a normal cycle, your temperature sits low through the first half, steps up after ovulation as progesterone rises, then falls back with your period. This biphasic curve is the anchor every temperature tracking method is built on, and wearable skin temperature captures it in about 4 in 5 cycles.
An anovulatory cycle is one where the step never arrives. No egg is released, so progesterone never climbs, and your temperature holds near its follicular phase level until the bleed. You can still bleed. The womb lining sheds for a different reason, so the period can arrive on time.
The Ultrahuman Ring reads skin temperature from your finger while you sleep. Each night is scored against your own baseline, not a population average.
If a cycle completes with no sustained rise, the Possible Anovulation flag appears after the cycle closes.
| Where you are | Ovulatory cycle | Anovulatory cycle |
|---|---|---|
| First half | Low and steady | Low and steady |
| Around ovulation | Starts to rise | No change |
| From ovulation to your next period | Held above baseline | Stays near baseline |
What the research says
Anovulation is more common than most women expect, and a normal-looking cycle doesn't rule it out.
A population study measuring progesterone in 1,545 Norwegian women during cycles of normal length found that only 63.3% of those cycles were ovulatory. More than a third had no ovulation at all, with no obvious sign from the calendar.
Energy is one driver. Researchers tracking daily hormones across 120 cycles in 67 exercising women found only half of those cycles ovulatory, with ovulation absent in 20.8%, compared to 95.8% ovulatory in a sedentary comparison group. Undereating, high training loads and low body weight all increase the odds of a skipped cycle.
Ongoing anovulation can also define polyendocrine metabolic ovarian syndrome (PMOS, until recently called PCOS), though many women with PMOS will still have ovulatory cycles. A meta-analysis of 24 studies found PMOS in around 10% of women under the Rotterdam criteria, with infrequent or absent ovulation in 15%.
What Ultrahuman's data shows
Possible Anovulation tracks more closely with irregular cycles than any other flag in Ultrahuman's dataset.
Across 1,297 cycles from 1,163 women aged 20 to 50, it separated irregular cycles from regular ones more sharply than any of the five other Cycle Flags, with odds ratios of 2.8 to 4.1 for the flag appearing in cycles from women reporting irregular cycles, and holding across every age group from 20 to 50.
How anovulatory cycle flags appear in the app
The flag appears in the Cycle Flags section of your Cycle & Ovulation page. Tap the flag for an illustration of the pattern; your own nightly skin temperature readings are on the Cycle Tracking page.
While an anovulatory cycle is common, frequent appearance across several cycles is worth raising with a doctor, especially alongside bleeds that are drifting lighter, cycles that are running longer, or periods that are starting to disappear.
Read the original research
All Studies →This explainer is based on original research by the Ultrahuman Science team. Explore the full Studies repository.
Frequently asked questions
Can I have a period without ovulating?
Yes. A bleed can happen when the womb lining sheds without an egg being released.
Is one anovulatory cycle something to worry about?
Usually not. A single skipped cycle after illness, travel or a stressful month is common, and cycles typically resume on their own. A repeated pattern is worth a conversation with your doctor.
Does the flag mean I can't get pregnant?
No. It describes one cycle that showed no temperature rise, nothing more. If you are concerned about your fertility, speak to your clinician.
Why did the flag appear on a cycle where I had other symptoms of ovulation?
The rise can be too small to clear your night-to-night variation, or a fever or week of missed wear can hide it. Temperature confirms ovulation better than it rules it out: treat the flag as a prompt rather than proof.
Can hormonal birth control cause the flag?
Hormonal contraception that suppresses ovulation removes the temperature step the flag looks for. A flat cycle is expected on it.
References
- Prior JC et al. Ovulation prevalence in women with spontaneous normal-length menstrual cycles: a population-based cohort from HUNT3, Norway. PLOS One 2015. PMID 26291617
- De Souza MJ et al. High prevalence of subtle and severe menstrual disturbances in exercising women: confirmation using daily hormone measures. Human Reproduction 2010. PMID 19945961
- Bozdag G et al. The prevalence and phenotypic features of polycystic ovary syndrome: a systematic review and meta-analysis. Human Reproduction 2016. PMID 27664216
- Shilaih M et al. Modern fertility awareness methods: wrist wearables capture the changes in temperature associated with the menstrual cycle. Bioscience Reports 2018. PMID 29175999
- Zhu TY et al. The accuracy of wrist skin temperature in detecting ovulation compared to basal body temperature. Journal of Medical Internet Research 2021. PMID 34100763
Cycle Flags describe associations in physiological data. They are not a medical diagnosis, a fertility test, or a contraceptive method. If your cycle changes in a way that concerns you, speak to your physician.
