What Neuroscience Tells Us About “Mommy Brain”

New mothers often report they are more forgetful, but what’s behind the phenomenon known as “mommy brain”?

Many new mothers report that their brains feel foggy during pregnancy and shortly after giving birth. They’re surprised at their memory lapses, forgetting things that they normally would be able to recall in a heartbeat. Enter “mommy brain,” a mysterious concept that is largely anecdotal to date, yet feels quite real and unnerving for postpartum women.

Researcher Diane Farrar explains, “Forgetfulness and slips of attention are phenomena commonly reported by pregnant women, but scientists have yet to identify a specific mechanism by which this memory impairment might occur. Indeed, some question whether the reported memory loss exists at all.”

Her research in 2010 shows that compared to average women, pregnant women and new mothers indeed do show poorer performance in spatial memory, the type that helps you trace your steps back to where you left those pesky keys. But we still don’t fully understand the biological and neurological underpinnings of mommy brain. Some theories link it to sex hormones, postpartum depression, and good ol’ sleep deprivation.

Brain Changes for Survival

That said, some studies suggest that there are measurable changes in a woman’s brain, behavior, and mental state after giving birth. And it’s a good thing it does, because it gives mothers and their babies a few indispensable survival advantages.

For example, an illuminating study by researcher Pilyoung Kim revealed that specific parts of a new mother’s brain grow rapidly during the first three to four months after having a baby. These regions are the amygdala, hypothalamus, and prefrontal cortex — areas involved in motivation and feel-good rewards, among other things. Essentially, the mother’s brain creates a strong drive to provide adequate food, sleep, and safety, and she’s rewarded with a heady rush of positive emotions when the baby is happy. Indeed, this strong drive can feel like a wholly-encompassing preoccupation.

Kim’s study also found that not every woman undergoes the same amount of postpartum brain growth, and the brain scans with less growth were more likely to belong to new moms who feel disconnected from their babies. The large-growth scans belonged to the enchanted, doting, gushing mothers who rated their babies picture-perfect in every way.

It’s true that all humans are wired to have a protective, positive, “awww” response to babies. But mothers in particular are attuned to their baby’s every coo and whim, thinking several steps ahead to anticipate future needs. The brain growth in new mothers provides support for the idea that when things get real, and a live human suddenly depends on them for survival, mothers’ brains have adapted to support and motivate them to provide unconditional, often obsessive care for their child.

As Kim told The Atlantic, “In new moms, there are changes in many of the brain areas. Growth in brain regions involved in emotion regulation, empathy-related regions, but also what we call maternal motivation — and I think this region could be largely related to obsessive-compulsive behaviors. In animals and humans during the postpartum period, there’s an enormous desire to take care of their own child.”

In light of this, “mommy brain’s” fuzzy-foggy forgetfulness makes more sense if new mothers need to reprioritize their cognitive resources to focus on the baby. They remember everything about their babies, and let other details of life fall by the wayside.

Mommy Brain Benefits Mother and Child

Other studies on new mothers’ brains have shown that over-the-moon motherly love relies on neural circuitry that overlaps with that of head-over-heels romantic love. And even the smell of a baby taps right into her brain’s pleasure centers. “These are the areas of the brain that are activated if you are very hungry and you finally get something to eat or if you are a drug addict and you finally get the drug you were craving,” says researcher Johannes Frasnelli. The effect is more powerful on new mothers than other women. (This was discovered during an adorable study where women sniffed scents from newborns’ pajamas.)

Researchers have also shown that mothers have a stronger positive response to their babies compared to any ol’ infant on the street (or even their friends’ babies, for that matter). This was demonstrated when mothers looked at photos of multiple babies―brain scans showed greater activity in areas like the amygdala and the thalamus when the photo was of their own child.

Interestingly, women whose amygdalas fired away the most when they looked at their babies were also less likely to have depression and anxiety, suggesting that postpartum brain changes not only help a mother care for her child, they also protect her own health and happiness.

It seems that “mommy brain” can be a lifesaver for both baby and mother: everyone benefits. Except the keys, forgotten on the coffee table.

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