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Mom Brain: More Than Meets the Eye

Mom Brain: More Than Meets the Eye

This is a guest post from Molly Mahler of Sleep Logics.


If I had a dollar for every time I said: ‘Whoops, sorry! Mom brain!” during my pregnancy and post-partum to excuse mistakes, mincing words, forgetting dates and so on…well, I’d be rich.

The term mom brain generally refers to common pregnancy and post-partum ‘isms’ including forgetfulness, being aloof, and general disorganization. It is often toted as a silly or cute aspect of pregnancy, and most of us don’t often think twice about why this happens. 

After 3 kids, 1 too many appointments missed, and inability to literally come up with the word “hamster” (What’s the name of that little rodent in kindergarten classes? With the wheel thing?) I wanted to know what the heck was going on.

What I found was shocking. Turns out, during pregnancy and after pregnancy, our brains SHRINK. Yes, they literally decrease in size. Originally, this was thought to reverse itself by 6 months post-partum, but more recent studies have determined that this does not completely reverse until closer to 2 years! 

It’s all starting to make sense now…

Researchers aren’t entirely sure why this happens. Many believe that pregnant bodies must adapt to allow for babies to grow and develop, therefore certain parts of the brain that aren’t critical for an infants survival just take a back seat for a while. Biology and evolution must play a role here, but that doesn’t make it any easier for mom. 

So, you have to birth a watermelon, recover, keep your newborn alive, deal with loads of hormones, not murder your husband/partner, manage a home, and do an abundance of other incredibly hard things with a smaller brain? OK biology, OK.

You would think there would be a built in mechanism to offset the brain shrinkage--like getting more sleep. Nope!

I would be remiss as a sleep coach not to mention the additional aspect of sleep loss and its role in perpetuating ‘mom brain’. Because newborns sleep in such small chunks for several weeks to months, moms often do not sleep long enough to enter REM sleep. 

REM sleep is responsible for learning, memory storage, and replenishing the good feeling hormones (dopamine and serotonin). Luckily, newborns usually jump right into REM when they fall asleep. But moms? Not so much. We have to get through at least 60-90 minutes of nonREM sleep before entering REM. 

Again, thanks a lot biology.

The best we can do is recognize that pre and post partum, we are literally not ‘firing on all cylinders’ and we need to give ourselves grace when we find ourselves frustrated and overwhelmed. Building a network of supportive friends, family, and even possibly 3rd parties such as a doula or sleep coach may alleviate the immense physical and mental burden of biology and physiology. 

I hope reading this brings some relief to moms who find themselves struggling to feel ‘normal’ or who feel that motherhood is disproportionately difficult. There is a reason for this, and it does not reflect your ability as a mother. You are a good mom. 

Moms are incredible. They are warriors. They figure out a way to carry on, brain shrinkage and all. I can’t think of anything more badass. 

Molly is an Occupational Therapy (MS) and Sleep Consultant. Her goal is to provide information and support to parents as they transition to parenthood. You can connect with Molly at

Oatridge A, Holdcroft A, Saeed N, Hajnal JV, Puri BK, Fusi L, Bydder GM. Change in brain size during and after pregnancy: study in healthy women and women with preeclampsia. AJNR Am J Neuroradiol. 2002 Jan;23(1):19-26. PMID: 11827871.
Barha CK and Galea LAM. The maternal 'baby brain' revisited. Nature Neuroscience. 20(2): 134-135 (2017).
Henry JF and Sherwin BB. Hormones and Cognitive Functioning During Late Pregnancy and Postpartum: A Longitudinal Study. Behavioral Neuroscience. 126(1): 73-85 (2017).
Hoekzema E, Barba-Müller E, Pozzobon C, Picado M, Lucco F, et al. Pregnancy leads to long-lasting changes in human brain structure. Nature Neuroscience. 20(2): 287-296 (2017).


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