So… is “mom brain” real?

Kind of—but probably not in the way the phrase suggests.

“Mom brain,” “baby brain,” and “pregnancy brain” are casual terms for the forgetfulness, distractibility, mental fog, and memory lapses many women report during pregnancy and early motherhood.

And the subjective experience is very real.

The scientific question is more complicated:

Are mothers actually performing worse on objective measures of cognition—or do they simply feel like their brains aren’t working the way they used to?

The answer depends partly on when you’re looking and what you’re measuring.

Pregnancy really does change the brain

This is the part we can say with considerably more confidence.

A landmark 2017 study followed women before and after their first pregnancies and found substantial changes in gray matter in regions involved in social cognition. The changes were specific to women who experienced pregnancy and persisted for at least two years in the study’s follow-up. The researchers also found that the degree of change was related to measures of maternal attachment.

That doesn’t mean women were “losing brain cells.”

Gray matter volume is not a simple score for intelligence.

Brain structure is constantly being remodeled. Changes in volume, thickness, connectivity, and organization can reflect the brain adapting to new demands.

A useful analogy is remodeling a house: removing a wall doesn’t necessarily mean the house has become worse. It may mean the space has been reorganized for a different purpose.

And pregnancy appears to be one of those periods of major remodeling.

Then came an extraordinary experiment

In 2024, researchers published one of the most detailed maps yet of the human brain during pregnancy.

They followed one healthy first-time mother from three weeks before conception through two years after birth, collecting 26 MRI scans along the way.

The results showed widespread reductions in cortical gray-matter volume and cortical thickness during pregnancy, while white-matter microstructural integrity increased. Some of these measures partially rebounded after birth.

The study is fascinating—but it also comes with a giant asterisk:

It was one person.

That makes it extraordinarily detailed, but not automatically representative of every pregnant woman.

Its real value is that it gives researchers an unusually detailed picture of what can happen and provides a roadmap for larger studies.

The researchers themselves describe it as a resource for understanding the highly dynamic neural remodeling that occurs during pregnancy.

It’s not just about gray matter

Another 2024 study followed 110 first-time mothers during late pregnancy and early postpartum, alongside 34 women who had not been pregnant.

Researchers found lower cortical volume across functional brain networks during late pregnancy, with those differences becoming less pronounced in early postpartum. Some networks appeared to recover more slowly than others. The researchers replicated the main findings in an independent sample.

And a 2022 study found pregnancy-related changes not only in brain structure but also in neural network organization and white-matter characteristics. Some of these changes were associated with pregnancy hormones and measures related to maternal-fetal bonding and responsiveness to infant cues.

So the picture emerging from neuroscience isn’t:

Pregnancy makes your brain smaller.

It’s closer to:

Pregnancy is a period of substantial neural remodeling.

That’s a very different statement.

But what about forgetting everything?

Here’s where the science gets messy.

A 2018 meta-analysis combined results from 20 studies involving 709 pregnant women and 521 non-pregnant women.

Overall, pregnant women performed somewhat worse on measures of cognitive functioning. The differences were most apparent in some measures of memory and executive function during the third trimester. Longitudinal analyses also found declines in general cognition and memory between the first and second trimesters.

So there is evidence that some cognitive changes can occur during pregnancy.

But the effects aren’t universal, aren’t enormous, and don’t appear across every cognitive task.

And that’s an important distinction.

You can have a statistically detectable difference in a memory test without suddenly becoming incapable of doing your job, remembering your children’s names, or functioning normally.

The postpartum story is even more complicated

Once the baby arrives, the variables multiply.

Sleep changes.

Hormones change dramatically.

Mood can change.

Daily routines disappear.

Attention is interrupted often.

And suddenly you’re trying to remember:

• whether you fed the baby

• where you put your phone

• what time daycare closes

• whether you ordered diapers

• why you walked upstairs

• and whether you actually turned the coffee maker off

Researchers have tried to separate biological changes from these environmental demands, but it isn’t easy.

One study of women during the first three weeks postpartum found that new mothers experienced more nighttime awakenings and that sleep-related measures were associated with memory and psychomotor performance.

In other words:

Sleep matters. A lot.

And then there’s the fascinating “I feel like my brain is worse” problem

A study of 86 women compared 43 first-time mothers approximately one year postpartum with 43 women who had never been pregnant.

The mothers reported significantly worse subjective memory.

But when researchers actually tested memory, working memory, processing speed, and other cognitive abilities, they found no significant differences between the mothers and non-mothers.

The mothers’ reports of poorer memory were associated with sleep, anxiety, and depression.

That doesn’t mean the women were imagining their experiences.

It means feeling cognitively impaired and demonstrating an impairment on a standardized test aren’t necessarily the same thing.

That’s an important distinction that gets lost in the “mom brain” conversation.

And because that particular study was a preprint rather than a final peer-reviewed publication, its findings should be interpreted cautiously.

So what’s actually happening?

The most honest answer is:

Probably several things at once.

Pregnancy changes the brain.

Motherhood changes your environment.

Sleep deprivation changes cognition.

Stress affects attention and memory.

Mood affects how we perceive our own cognitive performance.

And your brain is suddenly being asked to monitor an extraordinary number of variables simultaneously.

Some of what feels like “bad memory” may actually be attention overload.

If your brain never fully encoded where you put your keys because you were simultaneously listening for a crying baby, answering a work message, thinking about dinner, and wondering whether you remembered to move the laundry, retrieving the memory later is going to be difficult.

That’s not necessarily a broken memory system.

It may be an overloaded attention system.

The research doesn’t let us reduce the entire experience of motherhood to one explanation, and we shouldn’t try.

THE RESEARCH SAYS

Pregnancy is a period of substantial neuroplasticity.

Multiple longitudinal neuroimaging studies now show measurable changes in brain structure and organization during pregnancy. However, those structural changes should not automatically be interpreted as cognitive decline.