The Trouble with 'Mommy Brain'

Researchers are having trouble wrapping their heads around the memory-zapping phenomenon known as “mommy brain.” But one thing seems sure: changes in a woman’s brain after birth aren’t that dramatic—our lifestyles might be a bigger factor.


It was midway through my second pregnancy. My two-year-old daughter was sitting happily in the baby seat of the shopping cart. We’d managed to complete the weekly grocery shop without a single tantrum for the first time. All in all, as we headed back to the car, I was feeling pretty proud of myself on this particular day. Maybe I had this mom thing down after all.

That’s when I saw that the back door of the car was wide open. Had it been broken into? For a moment I panicked, but then—no. It was just another example of mommy brain. Also known as baby brain or pregnancy brain, it's perhaps best summed up by that foggy pregnancy feeling when your mind just goes to mush, and you cannot find your keys or remember why you went to the kitchen in the first place.

Like me, most new moms I know have experienced a ditzy moment or two. Oftentimes we (or our partners) chalk it up to sleep deprivation or sheer exhaustion. But does pregnancy lead to changes in the woman's brain that can actually be measured? And what are the implications of classifying this common phenomenon as biological or situational?

There’s a lot of conflicting research on what “mommy brain” actually is or does.

Certainly, scientists are bent on finding out. But until recently, a lot of the research has been focused on memory performance.

A 2010 study, for instance, found a link between pregnancy and diminished memory—particularly verbal recall memory, which is the ability to remember words and language.

Eight years later, research published in the journal Neurobiology of Learning and Memory used electroencephalography (EEG), a technique that records electrical activity in the brain, to determine that pregnancy affects the efficiency of visuospatial working memory. That’s where you temporarily store visual information and information about environment and orientation. That study found, you might be relieved to hear, that pregnancy and the postpartum period do not necessarily affect verbal working memory.

But what about the structure of the brain itself? Well, they’ve been studying that too—and it’s pretty confusing.

Research published by the American Psychological Association in 2010 found that a new mom’s brain can grow bigger after giving birth. Which seems like great news until you come across recent research that found the opposite—that the brain actually shrinks. Elseline Hoekzema, a neuroscientist from the Netherlands working in Spain, used MRI scanning to establish that pregnancy leads to changes in the brain that last at least two years.

Chief among these changes? A reduction in the volume of gray matter—as in, the all-important tissue that houses your nerve cells and is responsible for regulating your memory, emotions, and intellect.

Finally, a team of Australian researchers decided to investigate as well. Aiming to learn more about how pregnancy may change women’s brain functioning as they prepare for motherhood, the Baby Brain Research Project published its first study in the Medical Journal of Australia in January 2018. It confirmed that baby brain is indeed a real phenomenon.

Following a meta-analysis of 20 studies, the paper concluded that, “general cognitive functioning, memory, and executive functioning were significantly poorer in pregnant than in control women, particularly during the third trimester.” It also showed that pregnant women’s memory performance seems to decline between the first and second trimesters. So, if you find yourself becoming a bit forgetful at around the 12-weeks mark, you’re not necessarily imagining things.

Some of the research feels downright scary—but fear not.

Nobody wants to hear that pregnancy can actually make our brains get smaller—and excitatory newspaper headlines don’t help. It’s reassuring, then, to know that the cognitive changes we’re talking about are really very small, and the Deakin research showed that whenever pregnant women really need to focus on something, their cognitive function works just fine.

“The changes that we see tend to not be hugely significant changes,” said Sasha Davies, a principal investigator on the study, in a telephone interview. “It's not going to affect women's performance.”

Besides, the studies so far do not tell the whole story, and in fact the Baby Brain Research Project findings only served to reveal how much more research is needed. Having established that pregnancy is associated with cognitive changes, the team at Deakin is now conducting a further three studies. In particular, they’re looking into other life events that might have an impact on cognitive function—like stress or postpartum depression. To what extent are these brain changes due the stress and sheer exhaustion of becoming a mother, rather than the condition of pregnancy itself?

We have poor parental leave practice in the US, in addition to a family structure that does not often provide much support for parents of young children. If there is any ‘mommy brain’ here in the US, it’s likely a result of these factors, not simply that pregnancy intrinsically causes cognitive decline.
— Bonnie Jacob, mathematician and study author

Bonnie Jacob, a math professor at Rochester Institute of Technology in Rochester, NY, decided to investigate the phenomenon of baby brain soon after her first child was born. She found herself standing in front of the pantry with no idea of what she’d gone there to look for, and she wondered, “If motherhood impacts women’s intellect, what does that mean for my future as a mathematician?”

The result was a paper, published in the Journal of Humanistic Mathematics in July 2018, that pulled together much of the existing research, as well as the personal experiences of some of her fellow mom mathematicians. She’s firmly of the view that these other factors play a part.

“New parents in our society may simply be overwhelmed and exhausted,” she told me. “We have poor parental leave practice in the US, in addition to a family structure that does not often provide much support for parents of young children. If there is any ‘mommy brain’ here in the US, it's likely a result of these factors, not simply that pregnancy intrinsically causes cognitive decline.”

As it turns out, baby brain has an upside.

There’s a case to be made that cognitive changes in pregnancy actually have some benefits.

Hoekzema’s study concluded that the brain shrinkage in pregnancy is actually a good thing. The research found that the volume reductions showed “a substantial overlap with brain regions responding to the women’s babies postpartum.” Additionally, the changes predicted “measures of postpartum maternal attachment, suggestive of an adaptive process serving the transition into motherhood.”

In other words, if you do lose a bit of gray matter, it’s in the area of the brain related to social cognition. Any cognitive changes are the brain’s way of ramping up your ability to empathize, helping you to bond with your baby.

While new moms probably don’t need science to tell them that they’re feeling a little more empathetic following the birth of their baby, you could say the same about multitasking. It’s something that mothers just find themselves doing. While there’s no concrete scientific evidence of it yet, it’s something that researchers are keen to explore—particularly as it has been observed in rodents.

A 2012 article in Scientific American found that “no exact parallel to the PAG's [periaqueductal gray area’s] toggle function in rats has been identified in humans yet, but much has been made of a mother's superhuman ability to multitask, perhaps reflecting a similar adaptation.”

Why we should do away with the terms “mommy brain” or “baby brain” altogether.

While it can be comforting to discover that there’s a scientific reason for your temporary forgetfulness, the phrases “mommy brain” or “baby brain” can lead us into some pretty dangerous territory, particularly in the workplace. Pregnant women and new moms already face discrimination thanks to the mom brain stereotype, and scientific “proof” can make this perception worse.

Pregnant Then Screwed, a project that’s raising awareness of pregnancy discrimination, provides a platform for women to tell their stories. In the UK, it also offers a free legal advice phone line and lobbies the government for change. Joeli Brearley founded the organization after experiencing pregnancy discrimination herself, and she sees the term baby brain as “yet another tool to undermine” pregnant women and mothers.

“We know through research that pregnant women are seen as less competent and less committed than other types of employees,” she told me. “The nefarious notion that pregnant women have a ‘baby brain’ contributes to this negative bias and compounds any preconceived ideas that she is likely to become a burden to the workplace. Baby brain is seen as an affectionate slight, used regularly by men and women (including pregnant women themselves) without us really questioning the impact of those words.”

Pregnant women and new moms already face discrimination thanks to the mom brain stereotype, and scientific “proof” can make this perception worse.

When the Baby Brain Research Project published its first study last year, it attracted controversy almost immediately. Around two weeks after publication, Jacinda Ardern, the Prime Minister of New Zealand announced that she was having a baby, and the “baby brain is a real thing” story lent ammunition to critics who believed that her pregnancy made her unfit to stay in the job.

“People were using my research to say, ‘Well, you know, given that baby brain is a thing, we shouldn't be having her in office anymore,’ which is alarming. So it is a little bit concerning when we hear comments like that,” said Sasha Davies.

Davies herself is now pregnant, and while she might occasionally lose track of what she’s saying mid-sentence, it doesn’t affect her ability to do her job. And it’s made her even more determined to get across the message that her research should not be misused. “We do want to emphasize that as much as we're saying that there does seem to be a real change, it doesn't necessarily translate into notable performance deficits,” she said.

Cognitive changes during pregnancy are nothing to worry about—but that doesn’t make it any less annoying.

So if and when the fog descends, what’s the best way to deal with it?

Given that stress and lack of sleep play a part, prioritizing overall well-being comes pretty high on the agenda. What To Expect recommends some practical strategies, including writing down reminders for yourself, delegating jobs to other people, and, most importantly, taking a deep breath and going easy on yourself—it’s all about minimizing stress, remember?

There’s also a mineral that you might want to work into your daily diet. Choline, found in foods like eggs, milk, beef, and nuts, has been found to help improve postpartum brain function.

Finally, give yourself a break. Given all that new mothers are juggling, a little memory loss now and again is no biggie. As Bonnie Jacob puts it, “As I’ve struggled with balancing work and caring for small children myself while dealing with the typical sleep deprivation involved, I’ve been in awe of how well other mothers do! Amazingly, the mothers I know through work not only do it, but do it well.”

Susannah Cohen is a freelance writer with a background in fashion journalism and e-commerce. A mom of two, she recently moved from London to San Francisco, where she’s about to become an empty nester.