This article was medically reviewed by Kate Davies RN, BSc (Hons), FP Cert, Vice President Medical Women’s Health & Longevity at Ultrahuman.
Ovulation is the release of a mature egg from the ovary, usually once per cycle around the middle, and its most reliable signs are a change in cervical mucus to a clear, slippery, egg-white texture, a sustained rise in basal body temperature afterward, and a short surge in luteinising hormone (LH) just before. Some women also notice mild one-sided pelvic pain, a higher sex drive, or tender breasts, while others feel nothing at all. Reading these signals tells you when your fertile window is open, whether you’re ovulating at all, and when something is worth raising with a doctor. This guide covers the symptoms, the timing, and the most reliable ways to track ovulation, including for irregular cycles.
What are the signs of ovulation?
The body gives several signals around ovulation, though not everyone notices all of them.
- Cervical mucus changes — in the run-up to ovulation, cervical mucus turns clear, stretchy, and slippery, like raw egg white. This egg-white mucus precedes ovulation by one to three days and continues during the fertile time, which makes it one of the most useful real-time signals (Bigelow JL et al., Hum Reprod 2004, PMID 14990542).
- Basal body temperature (BBT) rise — after ovulation, rising progesterone nudges resting body temperature up by about 0.3°C. Because that happens after the egg is released, BBT confirms ovulation rather than predicting it (Reed BG & Carr BR, Endotext).
- The LH surge — luteinising hormone spikes roughly 24 to 36 hours before ovulation, and this is the signal ovulation predictor kits detect. These kits don’t work for everyone, though — in women with PMOS/PCOS, naturally raised baseline LH can trigger false positives.
- Mittelschmerz — some women feel a brief, one-sided ache low in the abdomen around ovulation (mittelschmerz, literally “middle pain”).
- Libido, breasts, and cervix — a higher sex drive, tender breasts, or a softer, higher cervix can track with the fertile window, though these are less consistent from person to person.
When do you ovulate, and how long is the fertile window?
In a textbook 28-day cycle, ovulation lands around day 14, but real cycles vary widely and the day of ovulation shifts with cycle length. The fertile window is the timespan when intercourse can lead to conception. It spans roughly the six days ending on the day of ovulation, because sperm can survive up to five days while the egg is viable for only about 12 to 24 hours (Wilcox AJ et al., N Engl J Med 1995, PMID 7477165). The highest-probability days are the two to three before ovulation, which is why pinpointing it matters. The menstrual cycle is increasingly recognised as a fifth vital sign, alongside heart rate, blood pressure, respiratory rate, and body temperature, and watching it over time is the clearest way to learn your own pattern.
How do you track ovulation?
No single method does everything, and they fall into two jobs. Some methods predict ovulation so you can time the fertile window; others confirm it after the fact so you know it actually happened.
- Cervical mucus monitoring predicts the fertile window, and in one study it was a better predictor of conception than timing of intercourse alone (Bigelow JL et al., 2004).
- Ovulation predictor kits (OPKs) detect the LH surge and flag ovulation a day or so ahead.
- Basal body temperature confirms that ovulation happened, but only after the fact.
- Cycle apps and wearables combine signals over time. A device that follows HRV across the cycle, skin temperature, and resting heart rate can surface the shift around ovulation without daily strips or thermometers.
Tracking ovulation with a wearable
A wearable makes cycle tracking continuous rather than a daily manual check. Skin temperature, heart rate variability (HRV), and resting heart rate all shift across the cycle, which lets a device estimate the fertile window and confirm ovulation. Ultrahuman’s Cycle and Ovulation Pro (C&O Pro) is built to both predict and confirm ovulation, which matters most when you’re trying to conceive and need the fertile window in advance, not just in hindsight. The OvuSense™ algorithm now powers C&O Pro, delivering more than 90% accuracy for ovulation confirmation from a skin-worn wearable (Hurst & Davies 2022). Confirming that ovulation has occurred is more reliable than pinpointing the exact day.
Pattern-detection features like Cycle Flags™ are best treated as a heads-up, not a diagnosis. They flag patterns worth paying attention to, especially when they show up across multiple cycles, and they make a useful conversation-starter with a doctor or specialist.
Ovulation with irregular cycles, including PMOS/PCOS
Irregular cycles make ovulation harder to pin down, and the most common reason is PMOS (polyendocrine metabolic ovarian syndrome)/PCOS (polycystic ovary syndrome), which affects 10–13% of reproductive-age women, with up to 70% of cases undiagnosed (World Health Organization). In PMOS/PCOS, cycles can stretch to 90+ days, and some are anovulatory (no egg is released).
Ovulation predictor kits are less reliable here, because baseline LH is often elevated in women with PMOS/PCOS, which can produce false positives. For that reason, the international PCOS guideline recommends pairing OPKs with at least one other ovulation signal (Teede HJ et al., Hum Reprod 2023, PMID 37580037). For long or irregular cycles, continuous skin-temperature tracking with C&O Pro is the most accurate method, since it works where calendar and kit methods struggle, and being able to predict ovulation (not just confirm it) is vital when you’re trying to conceive. Treatment for trying to conceive can include ovulation induction with medications such as letrozole or clomiphene, guided by a fertility specialist.
When to see a doctor
Tracking ovulation is also a way to identify when something needs attention. Consider seeing a clinician if you:
- have no signs of ovulation across several cycles, or cycles regularly longer than 35 days or shorter than 21
- have been trying to conceive for 12 months, or 6 months if you’re over 35, without success
- get severe ovulation pain rather than the brief, mild ache of mittelschmerz
- have very irregular or absent periods, which can point to PMOS/PCOS, thyroid issues, or other hormonal conditions worth investigating
Knowing your ovulation signs turns a guessing game into a pattern you can read, whether you’re trying to conceive, avoiding pregnancy, or simply understanding your body.
This article is for informational purposes and is not medical advice. Cycles and ovulation signs vary widely between individuals, so anyone with very irregular cycles, severe pain, or difficulty conceiving should consult a clinician. Disclosure: Ultrahuman sells the Ring AIR and Ring PRO, which track cycle-related signals (skin temperature, HRV, resting heart rate) that some women use to monitor cycle patterns, and Cycle and Ovulation Pro, a fertility-tracking platform built for complicated cycles, ovulation prediction, and pregnancy planning, with built-in cycle flags to help users understand cycle patterns and what they mean.
