Anovulation: Causes, Signs & What It Means for Pregnancy

11 min read
Anovulation: Causes, Signs & What It Means for Pregnancy

Anovulation simply means that an ovary doesn’t release an egg during a menstrual cycle.

It can happen occasionally without causing an ongoing problem. But if ovulation is repeatedly irregular or absent, periods may become widely spaced, unpredictable or disappear altogether, and becoming pregnant can be more difficult.

One important misconception is that irregular bleeding automatically means you aren’t ovulating. It doesn’t. Irregular periods can suggest irregular ovulation, but bleeding patterns alone can’t tell you with certainty whether an egg was released.

You can also experience bleeding during an anovulatory cycle, so seeing menstrual-like blood doesn’t always prove that ovulation occurred beforehand.

Key takeaways

  • Anovulation means an egg wasn’t released from an ovary during a particular cycle.
  • An occasional anovulatory cycle can occur, particularly during adolescence or perimenopause.
  • Repeated anovulation can cause late, irregular or absent periods.
  • Irregular periods suggest ovulation may be irregular but don’t prove anovulation.
  • PCOS is a common cause of chronic irregular ovulation.
  • Low energy availability, significant stress, thyroid conditions, high prolactin and other hormonal changes can also interfere with ovulation.
  • You can’t conceive during a cycle in which no egg is released, but people who ovulate unpredictably can still become pregnant.
  • Treatment depends on why ovulation isn’t occurring and whether pregnancy is wanted.

On this page

What is anovulation?

Ovulation is the release of an egg from an ovary.

In an ovulatory menstrual cycle, a follicle develops in the ovary, an egg is released and the remaining follicle becomes the corpus luteum.

The corpus luteum produces progesterone, which acts on the uterine lining during the second half of the cycle.

If pregnancy doesn’t occur, progesterone and oestrogen levels fall and menstruation follows.

With anovulation, an egg isn’t released.

Without normal ovulation and corpus luteum formation, the usual progesterone pattern doesn’t occur.

This can change how the uterine lining develops and sheds, which is why anovulatory cycles can produce irregular or unpredictable bleeding.

For more background, read our complete guide to the menstrual cycle.

Can you have a period without ovulating?

You can still bleed without ovulating.

Technically, menstrual bleeding follows an ovulatory cycle in which hormone levels fall at the end of the luteal phase.

But if ovulation doesn’t occur, the uterine lining can still become unstable and shed, causing bleeding that may look and feel like a period.

This is often described as anovulatory bleeding.

So neither of these assumptions is reliable:

  • “I bled, therefore I definitely ovulated.”
  • “My period was irregular, therefore I definitely didn’t ovulate.”

Your overall pattern and, when necessary, clinical testing provide more useful information.

What are the signs of anovulation?

Possible clues include:

  • long or widely varying menstrual cycles
  • frequently late periods
  • missing periods
  • unpredictable bleeding
  • very infrequent periods
  • difficulty becoming pregnant

Some people also have symptoms related to the underlying cause, such as acne or increased facial hair with PCOS, hot flushes with reduced ovarian function or symptoms of thyroid disease.

Anovulation doesn’t necessarily cause a symptom you can physically feel.

What causes anovulation?

Ovulation depends on coordinated hormonal signals between the brain, pituitary gland and ovaries.

Anything that substantially alters that signalling can affect ovulation.

Normal life-stage changes

Ovulation can be more irregular:

  • during the first years after periods begin
  • while breastfeeding
  • during perimenopause

This doesn’t mean every irregular cycle at these stages should automatically be ignored, particularly if bleeding is very heavy, prolonged or otherwise concerning.

PCOS

PCOS is one of the most common causes of chronic irregular ovulation.

Follicles may begin developing without one consistently reaching the point where an egg is released.

This may result in long cycles, infrequent periods or periods that disappear for months.

Low energy availability

If energy intake is consistently too low relative to the demands of exercise and everyday body functions, the brain may reduce reproductive hormone signalling.

This can lead to irregular ovulation and eventually amenorrhoea.

Significant stress

Physical or psychological stress can sometimes disrupt the hormonal signalling involved in ovulation.

Stress is only one possible cause, so recurring irregular cycles shouldn’t automatically be attributed to being busy or anxious.

Thyroid conditions

Both an underactive and overactive thyroid can affect menstrual cycles and ovulation.

High prolactin

Elevated prolactin can suppress hormones needed for ovulation.

This is normal during breastfeeding but can also occur because of some medicines or pituitary conditions.

Premature ovarian insufficiency

Reduced ovarian activity before age 40 can cause infrequent or absent ovulation.

Unlike menopause, ovarian activity can occasionally occur in people with premature ovarian insufficiency, so ovulation may be intermittent rather than permanently absent.

PCOS and anovulation

PCOS deserves particular attention because irregular ovulation is one of its central features.

You don’t necessarily have to miss periods completely.

Some people with PCOS ovulate occasionally and therefore have periods every few months. Others have cycles that vary considerably from one month to the next.

Pregnancy can occur even when periods are very irregular.

How do you know whether you are ovulating?

No single home sign is perfect.

Menstrual cycle tracking

Regular cycles make regular ovulation more likely but don’t prove that every cycle is ovulatory.

Very long or irregular cycles make irregular ovulation more likely.

Cervical mucus

Oestrogen often makes cervical mucus clearer, wetter and more slippery before ovulation.

This can be a useful fertility sign, but mucus alone can’t confirm that ovulation actually occurred.

Ovulation predictor kits

Ovulation tests detect a rise in luteinising hormone, or LH, that usually occurs shortly before ovulation.

A positive test predicts that the body is preparing to ovulate but doesn’t guarantee the egg was released.

They can also be more difficult to interpret in some people with PCOS because LH patterns may differ.

Basal body temperature

Progesterone after ovulation can cause a small rise in basal body temperature.

This can provide retrospective evidence that ovulation probably occurred but isn’t ideal for predicting ovulation in advance.

Blood tests

A progesterone blood test may be used to assess whether ovulation has occurred.

You may have heard this called a “day 21 progesterone” test, but day 21 only makes sense for a particular cycle length.

Progesterone is generally most informative when measured around a week before the next period is expected.

If cycles are very irregular, your doctor will determine appropriate timing.

Ultrasound

Ultrasound may sometimes be used as part of an investigation into irregular periods, PCOS or fertility.

Your doctor may also order tests for thyroid function, prolactin, ovarian hormones or other conditions depending on your symptoms.

Can you get pregnant if you don’t ovulate regularly?

If no egg is released during a particular cycle, pregnancy cannot begin in that cycle.

But there is an important difference between never ovulating and ovulating unpredictably.

Many people with irregular cycles still ovulate from time to time.

Because sperm can survive in the reproductive tract for several days, sex before an unexpected ovulation can result in pregnancy.

That means irregular or absent periods shouldn’t be treated as a reliable form of contraception.

If you’re trying to become pregnant, irregular ovulation can make timing more difficult but it doesn’t automatically mean you won’t conceive.

How is anovulation treated?

Treatment depends on the cause and whether pregnancy is currently wanted.

If low energy availability is contributing

Treatment may involve increasing energy intake, modifying training and addressing any disordered eating or other contributing factors with appropriate professional support.

If a thyroid or prolactin condition is involved

Treating the underlying hormone problem may restore ovulation.

If PCOS is involved

Treatment depends on your priorities.

If pregnancy isn’t currently wanted, management may focus on menstrual regularity, endometrial protection, acne, excess hair growth or metabolic health.

If pregnancy is wanted, treatment can focus specifically on inducing ovulation.

Ovulation induction

Ovulation induction uses medicines to help an ovary develop and release an egg.

For people with anovulatory infertility due to PCOS and no other infertility factors, the current international PCOS guideline recommends letrozole as the first-line pharmacological treatment for ovulation induction.

Other medicines or injectable fertility treatments may be appropriate in other circumstances.

These treatments need medical supervision because the appropriate medication depends on the cause of anovulation and fertility medicines can have risks, including multiple follicle development and, with some treatments, ovarian hyperstimulation.

What if you’re trying to conceive?

If your cycles are regular and you’re under 35, general fertility advice is to seek medical assessment after around 12 months of trying to conceive, or after around 6 months if you’re 35 or older.

But you don’t need to wait that long if your periods are very irregular or absent.

Irregular or absent ovulation is already a reason to speak with your GP earlier.

Your doctor may consider:

  • whether you are ovulating
  • PCOS or other hormonal causes
  • thyroid and prolactin levels
  • ovarian function
  • semen analysis for a sperm-producing partner
  • whether fallopian-tube assessment is appropriate

Fertility isn’t solely an ovulation issue, so it’s useful to assess the full picture rather than assuming irregular cycles are the only factor.

When should you see a doctor?

Speak with a GP if:

  • your menstrual cycles are repeatedly very long or unpredictable
  • your periods stop for 3 months or more
  • you have around 8 or fewer periods per year
  • you have symptoms suggesting PCOS
  • you have hot flushes or vaginal dryness well before the usual age of menopause
  • you have unexpected nipple discharge, headaches or vision changes
  • your periods stopped after significant changes in exercise or eating
  • you are trying to conceive and suspect you aren’t ovulating regularly

If your main concern is that your period has simply arrived later than expected, start with our guide to a late period when you’re not pregnant.

Frequently asked questions

What does anovulation mean?

Anovulation means an egg wasn’t released from an ovary during that menstrual cycle.

Can you have a period without ovulating?

You can have menstrual-like bleeding without ovulating. When ovulation doesn’t occur, the uterine lining may still thicken and later shed unpredictably. Bleeding alone therefore doesn’t prove that ovulation happened.

Do irregular periods mean you aren’t ovulating?

Not necessarily. Irregular cycles can indicate irregular ovulation, but some people with irregular cycles still ovulate. Testing or tracking over time may be needed to understand your pattern.

Can you ovulate without having a regular period?

Yes. People with irregular cycles may ovulate unpredictably. This is why pregnancy is possible even when periods are widely spaced.

Can stress stop ovulation?

Significant physical or psychological stress can interfere with the brain-hormone signalling needed for ovulation, but recurring anovulation has several possible causes and should not automatically be blamed on stress.

Can PCOS stop ovulation?

Yes. PCOS commonly causes ovulation to occur irregularly or not at all in some cycles. Many people with PCOS still ovulate occasionally and can become pregnant.

How do I know if I ovulated this month?

Cycle dates, cervical mucus, ovulation predictor kits and basal body temperature can provide clues but none is perfect. A correctly timed progesterone blood test or monitored ultrasound can provide stronger clinical evidence when necessary.

Can I get pregnant during an anovulatory cycle?

No. Pregnancy requires the release of an egg. However, if your cycles are irregular you may not know in advance whether a particular cycle will be anovulatory, so pregnancy can still occur if ovulation happens unexpectedly.

Can anovulation be treated?

Often, yes. Treatment depends on the cause. Addressing thyroid disease, high prolactin, low energy availability or PCOS may restore ovulation, while fertility treatment can induce ovulation when pregnancy is wanted.

What fertility medicine is used for PCOS?

For anovulatory infertility caused by PCOS where there are no other infertility factors, current international guidance recommends letrozole as the first-line medication for ovulation induction. Treatment needs to be prescribed and monitored by an appropriate healthcare professional.

Anovulation is a pattern, not a fertility verdict

Missing one ovulation doesn’t mean something is permanently wrong with your body.

Occasional anovulatory cycles can occur, particularly at times when reproductive hormone patterns are changing.

What deserves more attention is a recurring pattern of widely spaced or absent periods, difficulty conceiving or other symptoms suggesting an underlying hormonal condition.

Once the reason for irregular ovulation is understood, there are often useful treatment options, whether your priority is regulating bleeding, protecting long-term health or becoming pregnant.

Related reading

Sources and further reading

This article provides general educational information and isn’t a substitute for individual medical or fertility advice.