Oligoovulation: causes of infrequent ovulation

Author: Jessica Lloyd
Senior Vulvovaginal Speciliast Naturopath | BHSc(N) | ISSVD, ISSWSH, BSSM, ATMS

Last reviewed: June 26, 2026

Oligoovulation means you ovulate infrequently. Instead of releasing an egg roughly once a month, your ovaries do it now and then, with long or unpredictable gaps in between. In practice that usually shows up as cycles longer than 35 days, or fewer than eight or nine periods a year.

It is one of the most common reasons periods turn irregular, and one of the most common reasons it takes longer to fall pregnant. The good news is that infrequent ovulation is almost always a signal of something else going on – and once that underlying driver is found and treated, ovulation often comes back.

In our clinic, we see irregular ovulation often as a signpost to something upstream – an overworked stress system, a struggling thyroid, insulin running high, or hormones tipped out of balance. We look for and treat that upstream driver, and regular periods usually return.

What is oligoovulation?

Ovulation is the moment an ovary releases a mature egg. In a regular cycle this happens once per cycle, followed by a roughly two-week luteal phase and then a period. Oligoovulation is when that release happens less often than it should – sporadically, with long stretches where no egg is released at all.

There is no single hard cut-off, but most clinicians flag infrequent ovulation when cycles consistently run longer than 35 days, or when you have fewer than about eight or nine bleeds across a year. The 2023 international guideline on polycystic ovary syndrome defines ovulatory dysfunction as cycles shorter than 21 days or longer than 35 days once you are three years past your first period and before perimenopause.¹

It helps to separate three terms that often get tangled together:

Oligoovulation is about the ovulation event – eggs released infrequently.
Oligomenorrhoea is about the bleeding – infrequent or light periods, which is usually what you actually notice.
Anovulation means no ovulation at all in a given cycle.

They are linked, because the period you see is downstream of the ovulation you cannot. When ovulation is patchy, bleeding becomes patchy too. Oligoovulation also tends to be the milder end of a spectrum: in people with PCOS, those who ovulate occasionally have a gentler hormonal picture and respond better to ovulation-inducing treatment than those who do not ovulate at all.⁵

How do I know if I’m ovulating infrequently?

The most obvious clue is your cycle length. If your periods routinely arrive more than 35 days apart, skip months, or are wildly unpredictable, ovulation is the first thing worth looking at.

One thing worth clearing up: ovulation does not reliably happen on day 14. A real-world analysis of more than 600,000 cycles found an average cycle length of about 29 days, with the timing of ovulation varying widely from person to person and cycle to cycle.³ Most of the difference in cycle length comes from how long the first half – the run-up to ovulation – takes. So a long cycle very often means a delayed or missed ovulation, not a late period for no reason.

Other signs that ovulation may be infrequent include:

Periods that are months apart, or that you cannot predict at all.
No clear premenstrual pattern – the breast tenderness, mood shift or discharge change that tends to follow ovulation.
Trouble falling pregnant after several months of trying.
Flat or absent results on ovulation predictor kits month after month.

None of these confirms the cause on its own. They are the prompt to dig deeper, ideally with a clinician who can pair your cycle history with the right tests.

What causes oligoovulation?

Ovulation is the output of a finely tuned conversation between your brain and your ovaries – the hypothalamic-pituitary-ovarian axis. Anything that disturbs that conversation can make ovulation skip. These are the usual suspects.

Polycystic ovary syndrome

PCOS is the single most common reason for infrequent ovulation. It is diagnosed using the Rotterdam criteria, where irregular ovulation is one of three core features.¹

In PCOS, higher levels of androgens and, often, insulin resistance interfere with the final maturing and release of the egg. Follicles start to grow but stall before they ovulate. You can read more about the condition and its recent renaming in our dedicated guides.

A stressed or under-fuelled system

When the body senses it is under too much load – not enough food, too much exercise, significant weight loss, illness or sustained psychological stress – it can dial down the brain signals that drive ovulation to protect you.

At the far end this is called functional hypothalamic amenorrhoea, where periods stop altogether, but milder versions show up as infrequent ovulation long before periods disappear.²

This is the body doing something sensible in a difficult moment – pausing reproduction when conditions look poor. It is also one of the more reversible causes, because the fix is often about restoring energy balance and easing the load rather than a medication.

Thyroid and prolactin problems

The thyroid and the hormone prolactin both sit close to the cycle’s control panel. An under- or over-active thyroid can throw ovulation off, and so can raised prolactin, the hormone that normally rises in breastfeeding to suppress ovulation. This is why thyroid and prolactin blood tests are part of the standard work-up for irregular cycles.²

Approaching menopause, or just after your first period

Ovulation is naturally less reliable at the two ends of reproductive life. In the first few years after your first period the system is still calibrating, and skipped ovulations are common and usually normal. In the years leading into menopause – perimenopause – ovulation again becomes erratic as the ovary’s egg supply winds down. Cycle length and ovulation timing both drift with age, which large cycle-tracking data confirms.³

Premature ovarian insufficiency

Less commonly, the ovaries begin to run low on eggs early – before age 40. This is called premature ovarian insufficiency, and infrequent or absent ovulation can be one of the first signs. It is worth ruling out, particularly if cycles are getting further apart at a young age, because it has implications for fertility and long-term health.

Why infrequent ovulation matters

For most people the first concern is fertility, and that is reasonable: fewer ovulations across a year means fewer chances to conceive, and unpredictable timing makes those chances harder to catch. Infrequent ovulation is one of the leading reasons it takes longer to fall pregnant.¹

But there is a second reason it matters, and it is one people are rarely told about. Every time you ovulate, the second half of the cycle produces progesterone, which keeps the lining of the uterus in balance. When ovulation is infrequent, the lining is exposed to oestrogen without that regular progesterone counterweight – a state sometimes called unopposed oestrogen.

Over years, unopposed oestrogen can let the womb lining thicken too much. In people with PCOS, who frequently ovulate infrequently, the lifetime risk of endometrial cancer is roughly two to three times higher than average – still an uncommon outcome, but a real reason not to ignore long-term irregular cycles.⁴ You can read more in our guide to endometrial cancer.

The takeaway is not to panic about every long cycle. It is that persistently infrequent ovulation deserves a proper look, both to protect fertility and to keep the uterine lining healthy.

How oligoovulation is diagnosed and managed

Working out why ovulation is infrequent usually starts with a careful history – cycle pattern, weight changes, exercise, stress, medications and family history – followed by targeted tests. Hormone and blood testing typically looks at thyroid function, prolactin, androgens and markers of the ovarian reserve, sometimes with a pelvic ultrasound to see the ovaries and measure the womb lining.^1,2

Progesterone measured in the second half of the cycle can help confirm whether ovulation actually happened, though timing it is tricky when cycles are long and unpredictable.

Management follows the cause rather than the symptom, which is exactly how we approach it. Where the driver is energy deficit or over-training, the work is around nourishment, rest and load. Where it is PCOS, it may involve addressing insulin and supporting regular ovulation. Where thyroid or prolactin is to blame, correcting those often restores the cycle. For those trying to conceive, there are well-established medical options to bring ovulation back, prescribed and monitored by a fertility clinician.

What does not usually help is treating a long cycle in isolation without understanding why it is happening. The cycle is the readout, not the problem.

Frequently asked questions

Is oligoovulation the same as PCOS?

No. PCOS is the most common cause of infrequent ovulation, but it is not the only one. Thyroid problems, raised prolactin, stress and energy deficit, perimenopause and early ovarian decline can all do it. Oligoovulation is a pattern; PCOS is one possible explanation for it.

Can I still get pregnant if I ovulate infrequently?

Often, yes – it may just take longer, because there are fewer and less predictable opportunities each year. Many people with infrequent ovulation conceive, sometimes with help to encourage more regular ovulation. If you have been trying for several months without success, it is worth getting checked.

How can I tell when, or if, I’m ovulating?

Ovulation predictor kits, tracking your basal body temperature, watching for fertile cervical mucus, and a mid-luteal progesterone blood test can all help. When cycles are long and irregular these methods are less reliable, so pairing them with clinical testing gives a clearer picture.

Will my periods being irregular harm my health?

An occasional long cycle is normal. Persistently infrequent ovulation matters more, both for fertility and because long-term unopposed oestrogen can over-thicken the womb lining. That is a reason to investigate ongoing irregularity rather than wait it out.

Can infrequent ovulation fix itself?

Sometimes. Causes like stress, under-eating or over-exercise can resolve when the underlying load eases, and ovulation returns on its own. Others, like PCOS or a thyroid problem, usually need identifying and managing. Either way, finding the cause is the first step.

What to do next

If your cycles routinely run longer than 35 days, skip months, or have become unpredictable, treat that as useful information rather than a nuisance. Start tracking your cycles so you have a clear record to bring to an appointment, and ask about hormone and blood testing to look for a cause.

If you would like to talk it through, Aunt Vadge’s Assistant – the chat widget in the bottom left of your screen – can point you in the right direction, and our practitioners can help you work out what is driving infrequent ovulation and what to do about it.

This is general information, not a substitute for personalised medical advice. If irregular cycles are affecting your fertility or wellbeing, please see a qualified clinician.