Is Pregnancy Brain Real? A Pharmacist’s Deep Dive into the 2024 Nature Study
A few weeks ago, my wife was sitting on the couch looking for the TV remote.
"Honey, where did the remote go?"
It was in her hand.
We're 15 weeks into her pregnancy, and lately she's been forgetting things constantly. She'll open the fridge and completely blank on what she was looking for. Mid-sentence, a word will just vanish and she'll say, "You know — that thing! That thing!"
Most people call this "pregnancy brain." Moms-to-be laugh it off, partners shrug it off, and everyone chalks it up to hormones making things a little fuzzy.
I'm a pharmacist, so I figured I knew the basics — hormones, brain fog, totally normal. But recently I came across a study that genuinely surprised me. It was published in Nature Neuroscience in 2024 — one of the top neuroscience journals in the world — and it changed how I think about what's happening inside a pregnant woman's brain.
Here's the headline: Pregnancy physically changes a woman's brain. And not in a small way.
This isn't about mood or mindset. It's about real, measurable, structural changes. Let me break it down in a way that's easy to follow.
Infographic: How the brain streamlines gray matter and upgrades white matter during pregnancy (Based on Nature Neuroscience, 2024).
They scanned one woman's brain 26 times
The study followed a 38-year-old woman going through her first pregnancy (conceived through IVF). Researchers scanned her brain with MRI a total of 26 times — starting before she got pregnant and continuing until two years after she gave birth.
This wasn't a "scan before, scan after" situation. They scanned her regularly throughout the entire pregnancy, creating something like a time-lapse of her brain changing in real time.
Previous studies had mostly just compared before and after. This was the first time anyone had tracked the whole process this closely, week by week, month by month.
Quick brain anatomy — stick with me, it's useful
Before we get into the findings, here's a simple way to think about how the brain is structured. It'll make the rest of this make a lot more sense.
Think of the brain like a company:
Gray matter = the employees. These are your actual brain cells (neurons) — the ones doing the thinking, remembering, feeling, and decision-making. They're clustered in the outer layer of your brain (the cortex) and in some deeper structures.
White matter = the company's internal communication network. These are the "cables" that connect brain cells to each other and allow them to send information back and forth. They're wrapped in a white fatty coating called myelin — hence the name.
So: gray matter = the workers, white matter = the network connecting them. Both of these change during pregnancy — but in completely opposite directions. That's the big story here.
Wait — does pregnancy shrink your brain?
Sort of. As pregnancy progressed, the volume of gray matter in this woman's brain decreased. The outer surface of the brain also got slightly thinner. Changes were detected in roughly 80% of the brain's 400 regions — so this wasn't isolated to one spot. Nearly the whole brain was affected.
But before you panic:
Smaller does not mean worse.
Think about a brand-new smartphone loaded with bloatware — apps you've never opened and never will. If you clear out the clutter, the storage number goes down, but the phone actually runs better. Researchers describe what happens in pregnancy as "fine-tuning" — the brain reorganizing and streamlining itself for its new role.
Earlier research has even found that the more a woman's brain changes during pregnancy, the stronger the emotional bond she tends to form with her baby after birth.
Which parts of the brain change the most?
Not every brain region changes equally. Here are the areas that showed the most significant changes (the brain changes at different rates throughout the three trimesters of pregnancy):
| Brain Region | What It Does | Change During Pregnancy |
|---|---|---|
| Inferior parietal lobe | Attention, understanding others | Volume decreased (rapidly) |
| Insula | Emotional awareness, empathy | Volume decreased (rapidly) |
| Prefrontal cortex | Rational thinking, decision-making | Volume decreased (rapidly) |
| Somatosensory cortex | Processing touch, temperature, pain | Volume decreased (rapidly) |
| Ventral diencephalon (includes hypothalamus) | Core instincts, maternal behavior | Largest decrease of all |
| Hippocampus | Memory formation, spatial awareness | Volume decreased |
The most striking change happened in the ventral diencephalon, which includes the hypothalamus. This is the part of the brain that controls basic survival functions like body temperature, appetite, and sleep — but in animal studies, it's also the key hub for triggering maternal behavior. In mice, when this region is remodeled during pregnancy, mothers become more sensitive to the sounds and smells of their pups.
In other words, the brain isn't getting worse. It's getting rewired for motherhood.
As for the hippocampus — that's your memory center. Its shrinkage during pregnancy is likely one of the main reasons "pregnancy brain" actually happens. If the part of your brain responsible for forming memories is in the middle of a renovation, some forgetfulness comes with the territory.
But something gets stronger
While the gray matter (the workers) was scaling back, something else was getting a serious upgrade.
The white matter — the communication network — was getting measurably stronger. The quality of these connections improved significantly during the first and second trimesters.
You've reduced the headcount a bit, but you've upgraded the entire internal communication system to fiber-optic. The company runs leaner, but faster.
One of the pathways that was specifically strengthened connects visual processing to emotional processing. Researchers think this might be the brain pre-loading itself — getting ready to quickly read and respond to a baby's expressions and cries after birth.
Here's the overall picture:
Summary: How the brain changes during pregnancy
| Brain Component | Change During Pregnancy | Analogy |
|---|---|---|
| Gray matter (neurons) | Volume decreases | Clearing out unused apps |
| White matter (connections) | Quality improves | Upgrading from 3G to fiber-optic |
| Ventricles (fluid-filled spaces) | Volume increases | Temporary space cleared for construction |
The culprit: hormones on a rocket ship
Everything you just read was driven by hormones.
During pregnancy, estrogen (estradiol) and progesterone levels can spike anywhere from 100 to 1,000 times their normal levels. In this study, the woman's estradiol was 3.42 pg/mL before pregnancy. Three weeks before giving birth, it hit 12,400 pg/mL. That's roughly a 3,600-fold increase.
After delivery? It dropped to 11.50 pg/mL.
Hormones shoot up like a rocket — then freefall the moment the baby arrives.
Every brain change in this study — the gray matter reduction, the white matter strengthening, the fluid-space expansion — tracked statistically alongside those hormone fluctuations.
As a pharmacist, I want to add something here: estrogen and progesterone aren't just "female hormones" in the way most people think of them. They're also powerful neurological agents. They influence neuron growth, synaptic connections, immune cell activity, and the insulation wrapping around nerve fibers. Every nutrient a pregnant woman takes in is, in some sense, raw material for this massive brain remodel. If you're wondering how to time your prenatal supplements for maximum effect, I put together a pharmacist's guide to prenatal supplement schedules that might be worth a read.
Does the brain go back to normal after birth?
Some things do. Some things don't.
The white matter improvements reversed after delivery, returning toward pre-pregnancy levels. The fluid-space expansion also shrank quickly. But the gray matter reduction and cortical thinning did not fully recover even two years after birth.
Other studies have found these changes can persist for six years post-birth — and that traces of them can be detected decades later.
Pregnancy leaves a permanent mark on the brain. And that mark isn't damage — it's evidence of transformation.
This is also why some postpartum fogginess is completely normal. The brain is still finishing its renovation. Rest matters. Asking for help matters. Be patient with yourself — and with the new moms in your life. (If you're in the postpartum phase and navigating feeding decisions, here's a practical guide to breastfeeding duration based on WHO and AAP guidelines.)
How does this compare to a non-pregnant brain?
The researchers also tracked 8 healthy adults who weren't pregnant over a similar period — for comparison.
The results were striking. The gray matter changes in the pregnant woman were 3 times larger on average than in non-pregnant adults. In specific regions of the hippocampus, the changes were 3 to 4 times larger. And compared to the woman's own pre-pregnancy baseline, the magnitude of change was 6 times greater.
This is not normal brain fluctuation. This is a completely different category of change.
It looks a lot like puberty
Here's something the researchers found fascinating: the brain changes during pregnancy mirror what happens during adolescence.
During puberty, sex hormones surge, gray matter decreases, and white matter strengthens. The result? Improved executive function (planning, judgment) and better social cognition (reading other people's emotions). The brain becomes more efficient and socially attuned.
Pregnancy follows the same script. Hormones surge, the brain restructures, and the result is a brain that's wired for parenthood — more sensitive to a baby's needs, more emotionally in tune, more prepared for the demands of raising a child.
If puberty is the brain's transformation from child to adult, then pregnancy is its transformation from adult to parent. And in both cases, the brain is the one driving the change.
Why does this research matter?
Around 140 million women become pregnant every year worldwide. Roughly 85% of women will be pregnant at least once in their lifetime. And yet research on what happens to the brain during pregnancy has been remarkably sparse.
This study only followed one woman, so we can't assume every pregnancy looks exactly like this. The researchers are upfront about that. But the potential implications are significant.
For example: postpartum depression affects about 1 in 5 new mothers. If we can track brain changes during pregnancy, we might be able to identify women at higher risk before symptoms even appear.
The research could also shed light on why certain neurological conditions — like epilepsy, migraines, and multiple sclerosis — sometimes get better or worse during pregnancy. For anyone wondering what's actually safe to take during this time, I've also written a pharmacist's guide to safe medications during pregnancy.
What I took away from all this — as a husband
After reading this paper, I looked at my wife differently.
The woman holding the remote while searching for it. Standing in front of the open fridge with a blank look. Trailing off mid-sentence because the word just... left.
She's not being absent-minded. Her brain is under major construction.
She's building a baby's organs from scratch. At the same time, she's reorganizing her own brain — pruning gray matter, strengthening neural connections, riding a hormonal wave that dwarfs anything the human body normally experiences.
Pregnancy isn't just growing a baby. It's a complete rebuild of the person doing the growing.
So the next time you notice a pregnant woman forgetting something, maybe skip the "Wow, you're so forgetful lately" comment. Try this instead:
"Your brain is literally upgrading right now. A little lag is totally expected."
What's your best "pregnancy brain" story? Whether it happened to you, your partner, or someone you know — did anyone put their phone in the freezer? Wash the remote with the laundry? I'd love to hear it in the comments.
Reference: Pritschet, L., Taylor, C.M., Cossio, D. et al. Neuroanatomical changes observed over the course of a human pregnancy. Nat Neurosci 27, 2253–2260 (2024).
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