Does Your Uterus Change Size During Your Menstrual Cycle?

13 min read
Two clay models representing the uterus

Does your uterus change size during your menstrual cycle? It may change somewhat, but probably not as dramatically as some popular claims suggest.

Limited ultrasound research has found changes in the dimensions of the uterus across the menstrual cycle. What is much better documented, though, is what happens to the uterine lining, or endometrium, which sheds, rebuilds and changes in response to hormones throughout the cycle.

Many people also describe their lower abdomen or pelvis as feeling heavier, fuller, swollen or more noticeable before or during their period. Those sensations are real, but they don't necessarily mean the uterus itself has become dramatically larger. Uterine contractions, bloating, fluid retention, bowel changes and pelvic pressure can all contribute to how your body feels at different points in your cycle.

So while your uterus isn't completely static, there isn't good evidence that it routinely doubles in size or weight every month.

Key takeaways

  • The uterus may change somewhat across the menstrual cycle, but research on whole-uterus size is limited.
  • The uterine lining changes much more predictably. The endometrium sheds during your period and rebuilds during the cycle.
  • There is no good evidence that the uterus routinely doubles in size or weight each month.
  • Feeling heavier or fuller before or during your period is a common experience, but sensation alone can't tell us how much the uterus has changed.
  • Bloating, bowel changes, fluid retention and uterine contractions can all contribute to pelvic heaviness or a swollen feeling.
  • Uterus size isn't a useful way to choose a menstrual cup or disc. Cervix height, vaginal anatomy, product dimensions and comfort matter more.

Contents

Does the uterus really double in size during your period?

Probably not.

You may have seen social media posts or graphics claiming the uterus doubles in size or weight at different points in the menstrual cycle. Some even give a different uterus length and weight for each phase.

We couldn't find good research supporting those figures as something that routinely happens across a menstrual cycle.

That doesn't mean the uterus never changes at all.

The uterus is a muscular organ that responds to changing hormones, and a small ultrasound study has found measurable changes in uterine dimensions across ovulatory cycles. The evidence is limited, though, and it doesn't support a simple pattern where everybody's uterus predictably doubles in size before shrinking again.

The much clearer changes happen in the endometrium, the lining inside the uterus.

It's useful to separate two different things:

  • Uterine size: the dimensions or volume of the whole uterus, including its muscular wall.
  • Endometrial thickness: the thickness of the lining inside the uterus.

The endometrium can change considerably without the whole uterus changing by anything like the same proportion.

What happens to the uterus during each menstrual phase?

The menstrual cycle is commonly described in four phases: menstruation, the follicular phase, ovulation and the luteal phase.

These aren't four completely separate blocks. In particular, the follicular phase begins on the first day of your period and continues until ovulation.

A typical adult cycle is usually around 21 to 35 days. A 28-day cycle is often used as an example, but your cycle doesn't need to be 28 days and ovulation doesn't reliably happen on day 14.

For a broader explanation, see our guide to the menstrual cycle.

Menstruation: the uterine lining sheds

Day 1 of your menstrual cycle is the first day of your period.

If pregnancy hasn't occurred, oestrogen and progesterone levels fall and the functional layer of the endometrium begins to break down and shed.

Blood, endometrial tissue and other fluid pass through the cervix and vagina as menstrual fluid.

The uterus also contracts to help move this material out, and those contractions contribute to period cramps and may be part of the reason your pelvis feels heavier or more noticeable during your period.

As menstruation progresses, the endometrium becomes thinner. That doesn't mean the entire uterus suddenly shrinks to a predictable minimum size.

Read more about the menstrual phase.

Follicular phase: the lining rebuilds

The follicular phase begins on the first day of your period and continues until ovulation.

Follicles develop in the ovaries and rising oestrogen encourages the endometrium to rebuild after menstruation.

Ultrasound research has documented increases in both endometrial thickness and endometrial volume through this part of the cycle.

That's much better established than a particular increase in the length, width or weight of the whole uterus.

Read more about the follicular phase.

Ovulation: an egg is released

Ovulation happens when an ovary releases an egg, usually following a surge in luteinising hormone, or LH.

The timing varies between people and from one cycle to another.

By around ovulation, the endometrium has generally become thicker than it was immediately after menstruation.

Some ultrasound studies suggest endometrial growth begins to level off around this stage. That doesn't mean the whole uterus reaches a universal maximum size on ovulation day.

Read more about the ovulatory phase.

Luteal phase: the lining changes in preparation for possible pregnancy

After ovulation, the follicle that released the egg becomes the corpus luteum and produces progesterone.

Progesterone changes the endometrium so it becomes more glandular and secretory, helping create conditions that could support implantation if pregnancy occurs.

The uterine lining doesn't necessarily continue getting progressively thicker throughout the entire luteal phase. Studies using ultrasound have reported slightly different patterns, although several suggest endometrial volume reaches a plateau around ovulation or during the luteal phase.

If pregnancy doesn't occur, hormone levels fall and the next period begins.

Read more about the luteal phase.

What does ultrasound research tell us about uterus size?

Ultrasound can be used to measure both the uterus and the endometrium. Three-dimensional ultrasound can also estimate volume.

Research suggests that both can change across the cycle, but the evidence is much stronger for changes in the endometrium.

Some research has found changes in the whole uterus

A small 1975 study used ultrasound to measure uterine size throughout ovulatory menstrual cycles in 16 women.

The researchers reported that uterine size increased towards the end of the menstrual cycle.

This suggests the uterus itself isn't necessarily completely static throughout the month.

However, the study was very small and used ultrasound technology from more than 50 years ago. It doesn't establish one pattern for everybody and doesn't support the popular claim that the uterus routinely doubles in size or weight.

Changes in the uterine lining are much clearer

A 1997 study used three-dimensional ultrasound to follow endometrial and uterine volumes through menstrual cycles. Data from 18 participants were analysed and the researchers found cyclical changes in endometrial volume.

A 2004 study followed 30 women through their cycles using three-dimensional ultrasound. It found that endometrial thickness and volume increased significantly during the follicular phase, reached a plateau around ovulation and remained relatively stable through the luteal phase.

These studies were relatively small and used different methods, so they don't give us one universal set of measurements that applies to everybody.

The fairest conclusion is that the uterus may change somewhat across the cycle, while changes in the endometrium are much more clearly established. There isn't good evidence for a routine doubling in the size or weight of the whole uterus.

Why uterus size varies between people

There's also no single uterus size that's right for everybody.

Overall uterine dimensions can vary with factors such as:

  • age
  • pregnancy and childbirth history
  • hormonal status
  • menopause
  • fibroids
  • adenomyosis
  • other conditions affecting the uterus

These differences between people are another reason not to assign one set of measurements or weights to each menstrual phase.

Why can your pelvis feel heavier or fuller during your period?

This is where personal experience is worth acknowledging.

Many people describe feeling heavier, fuller, swollen or more aware of their lower abdomen or pelvis before or during their period. Some describe it as though their uterus itself feels heavier.

That experience shouldn't be dismissed just because we can't measure exactly what's creating the sensation.

What we can't do is use that feeling alone to say how much the uterus has increased in size.

Several things may contribute to a heavier or fuller feeling around your period, including:

  • uterine contractions as the uterus helps expel menstrual fluid
  • changes in the uterine lining
  • fluid retention
  • bloating and changes in bowel function
  • pelvic floor muscle tension
  • general pelvic sensitivity or pressure

For some people, several of these things may be happening at the same time.

Conditions affecting the uterus can also create a more noticeable feeling of pelvic pressure or fullness.

Fibroids can enlarge the uterus and may cause heavy bleeding, pelvic pressure or a feeling of fullness.

Adenomyosis involves endometrial-type tissue growing into the muscular wall of the uterus and can cause the uterus to become enlarged or tender, along with painful or heavy periods.

So if your pelvis feels different during your period, the sensation itself is real, but it doesn't automatically mean the normal menstrual cycle has caused your whole uterus to dramatically enlarge.

Read our guide to managing period bloating for practical suggestions.

If pelvic pressure, bloating or heaviness is persistent, getting worse or affecting everyday life, speak with a GP or another qualified healthcare professional.

Can uterus size affect menstrual cup or disc fit?

Uterus size isn't a particularly useful guide when choosing a menstrual cup or disc.

The uterus sits above the cervix. Menstrual cups and discs are worn within the vagina, so the overall size of your uterus isn't the same thing as the space available for a period product.

Factors that are more useful include:

  • cervix height and position
  • vaginal anatomy
  • product length and diameter
  • cup or disc shape
  • firmness
  • comfort and pressure sensitivity
  • menstrual flow
  • previous experience with internal products

Your cervix may also feel higher or lower at different points in your cycle.

Some people notice a clear pattern in their own body while others don't. Research hasn't established one cervix-height pattern that applies to everybody, so checking your own cervix through your cycle can be more useful than relying on a diagram.

Our guide to measuring your cervical position explains how.

Once you have an idea of your cervix height, you can explore our high cervix options and low cervix options, or browse menstrual cups and menstrual discs.

Our guide to choosing a menstrual cup size may also help.

When should you seek medical advice?

You don't need to monitor or measure the size of your uterus through your menstrual cycle.

It's worth speaking with a GP or another qualified healthcare professional if you experience:

  • period pain that is severe, worsening or regularly interrupts everyday activities
  • bleeding that is much heavier than your usual pattern
  • persistent pelvic pressure, fullness or heaviness
  • bleeding between periods
  • bleeding during or after sex
  • new or worsening pelvic symptoms
  • any vaginal bleeding after menopause

These symptoms have several possible causes. Conditions such as fibroids, adenomyosis and endometriosis can all affect the uterus and pelvis in different ways.

A healthcare professional can assess your symptoms and decide whether an examination, ultrasound or another investigation would be useful.

See healthdirect's heavy periods information if bleeding is a concern.

Seek urgent medical attention for sudden severe pelvic or abdominal pain, particularly if you also have heavy bleeding, dizziness, fainting or pregnancy may be possible.

Frequently asked questions

Is the uterus bigger before your period?

Possibly. Limited ultrasound research suggests the uterus itself can change somewhat across the menstrual cycle, including becoming larger towards the end of some ovulatory cycles. However, the research is limited and there isn't one predictable size pattern that applies to everybody.

Why does my uterus or pelvis feel heavy during my period?

Many people describe a heavier, fuller or swollen feeling around their period. Uterine contractions, changes in the uterine lining, bloating, fluid retention, bowel changes and pelvic floor tension may all contribute. The feeling itself can't tell you how much the uterus has changed in size.

Does your uterus shrink when you have your period?

The endometrium becomes thinner as it sheds during menstruation. The whole uterus may also vary somewhat in size across the cycle, but it doesn't suddenly shrink by a large or predictable amount when your period starts.

Does your uterus double in size during your period?

There isn't good evidence that the uterus routinely doubles in size or weight during a menstrual cycle. Small cyclical changes in the uterus may occur, while changes in the uterine lining are much better established.

How thick does the uterine lining get during a menstrual cycle?

Endometrial thickness varies with cycle stage, age, hormones and individual anatomy. It is generally thinner around menstruation and increases during the follicular phase. There isn't one measurement that's normal for everyone, and ultrasound measurements need to be interpreted in context by a healthcare professional.

Can you feel your uterus changing size?

You may notice changes in pelvic pressure, fullness, bloating or cramps during your cycle, but these sensations can't reliably tell you how much the uterus itself has changed in size.

Does hormonal contraception change what happens to the uterine lining?

Yes. Hormonal contraception can change ovulation and the way the endometrium grows and sheds. The effect depends on the method, so the natural cycle-phase descriptions in this article won't necessarily apply while using hormonal contraception. See our guide to contraception options in Australia.

Understanding what you feel without overstating what we know

Your uterus isn't completely static throughout the menstrual cycle, and it's reasonable that your pelvis may feel different at various points in the month.

Research suggests the uterus itself may change somewhat, while the much clearer and better documented changes happen in the endometrium: it sheds during menstruation, rebuilds during the follicular phase and changes after ovulation in preparation for a possible pregnancy.

At the same time, many people genuinely feel heavier, fuller, more bloated or more aware of their pelvis before or during their period.

We don't need to dismiss those experiences just because they can't be explained by a simple โ€œyour uterus doubles in sizeโ€ claim.

Our bodies are a little more complicated than that.

If you'd like to understand your own patterns, try Period Shop's free downloadable period tracker.

Related reading

Sources and further reading

This article provides general menstrual health information and isn't a substitute for personalised medical advice.