Parenthood Changes Our Brains. Emerging Research Tells Us How — And How Much

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During adolescence, children and teenagers undergo puberty, in which their brains, bodies and psyches are being reshaped. The majority of the human population will experience a third life event that can usher in changes of a similar magnitude, and that is the transition to parenthood.

For generations, new moms and dads have described feeling fundamentally changed by the arrival of a baby. It’s only recently that scientists have been able to see that change in the brain itself. Although that research is still in its early days, the findings are clear: Pregnancy and new parenthood leave lasting marks on a person’s brain, especially a mother’s.

Susana Carmona, one of the foremost researchers on “matrescence” — a term that refers to the developmental transition associated with becoming a mother, akin to adolescence — has found that pregnancy and the postpartum period are associated with a pronounced reduction in gray matter volume in the brain, averaging about 5%.

But Carmona, director of a neuroimaging lab in Madrid and author of the book “ A Mother’s Brain: The New Science of the Neuro-Maternal Revolution ,” cautions against leaning into tropes about “mommy brain” and “pregnancy brain,” which suggest that women become less sharp, less capable and more forgetful as they enter motherhood.

“These changes, far from being evidence of any cognitive problems, facilitate mother-baby bonding,” Carmona writes in her book, which was published on Oct. 6. “In neuroscience, as in many other parts of life, less can be more.” It’s not unlike the way a movie is produced or a book is edited.

The raw material gets edited down until a clearer, more focused story emerges. A pregnant mother’s brain is pruning itself to prepare for the heightened responsibilities ahead. Carmona, who has conducted a decade of research on this topic and contributed to more than 60 peer-reviewed publications, has found that the brain-shrinking that occurs in pregnancy is concentrated in regions responsible for self-reflection, social cognition and empathy.

These adjustments, Carmona said, allow a mother to be more attentive to her baby and more responsive to the baby’s needs. One effect, she has found, is that stimuli from babies, such as crying or fussing, become “super salient for mothers,” alerting them to their child’s unmet need or possible danger.

A mother whose baby is crying may find it nearly impossible to focus on anything else until she can soothe her child. Breastfeeding mothers, Carmona noted, will sometimes experience the letdown reflex, in which milk is released without a latch, simply from hearing a baby cry — and it need not even be their own baby.

“Baby stimuli are so relevant they’re able to catch our attention,” Carmona said. “They are able to kidnap our resources. ... It kind of ensures the mother is in contact with the baby.” The brain changes that a mother undergoes are so dramatic that a computer reviewing brain scans could tell, with 100% accuracy, whether a woman had been pregnant, Carmona and her team found.

The full gamut of neurological changes are detectable by the end of pregnancy, just before birth. They rebound partially in the first month postpartum, though some brain changes can still be observed six years later. One of the ways that a mother’s brain is different from that of a woman without children is that it appears younger, even decades on.

That anti-aging trend grows stronger with each subsequent child — up to a point. “At around four children, her cognitive capacity and cerebral youth start to decline again,” Carmona writes in her book. There are different hypotheses for why mothers’ brains end up looking more youthful.

“Taking care of a baby and a toddler and later a child — it’s like doing constant sudoku,” Carmona said, offering one explanation. “It’s like training your brain at a gym, in a highly demanding environment.” Research on women during a second pregnancy can offer a clue, Carmona said, citing work from her Dutch colleague Elseline Hoekzema.

Though their brains don’t change much beyond how they did during the first pregnancy, some additional regions of the brain are altered, Carmona said, including those focused on divided attention (or the brain’s ability to process multiple inputs at the same time). Carmona, who is herself a mother, loves that her research puts evidence to ideas that mothers have long known.

Now she wants the rest of the population to start to appreciate the role mothers play. “Our society does not value what we’re doing. It’s the essence of the survival of our species, [yet] they have turned it to something minimal,” she said, referring to ideas such as “ mommy brain ” and “ momnesia .” Mothers, she noted, are often sleep deprived and juggling a heavy mental load, keeping track of their baby’s naps and wake windows, feedings, diaper changes, exposure to illness and much more — like a computer with thousands of tabs open.

“Instead of focusing on the fact we’re doing something really amazing, it’s making a joke of it. You have to deal with all of that after creating a human from scratch,” she added. Carmona’s research — and other studies focused on matrescence — shows that women’s brains change during pregnancy to prepare them to be more attentive, motivated caregivers to their children at birth.

But that is not the only path to being a great caregiver. Emerging research shows that fathers and other nonbirthing parents can experience brain changes at the transition to parenthood as well. “Pregnancy is a physiological event — our breasts change, our bodies change, our brains change,” Carmona said.

“Fathers can arrive through a different route.” That route, she said, comes from being involved in the caregiving: changing diapers, bathing the baby, bottle feeding, doing skin-to-skin contact. “The more time they spend with the baby, the more their hormones will change,” she said, referencing research from psychologist Darby Saxbe of the University of Southern California.

In her book “ Dad Brain: The New Science of Fatherhood and How It Shapes Men’s Lives ,” which was published in May, Saxbe shares her research on fathers conducted during their partners’ pregnancy and in the first year of their child’s life. Saxbe scanned the men’s brains, tested their hormone levels and interviewed them about becoming parents.

She asked them how much time they spent with their baby and how much of that time was as the primary caregiver; she asked about their paternity leave options, as well as how close they felt to their baby and how competent they felt as a father. Saxbe found that fathers, too, undergo brain changes as they approach parenthood.

Samples of men in both California and Spain showed shrinkage in the same regions of the brain as mothers. Their loss in gray matter volume is less pronounced than mothers’ — about 1% in the small sample she took — but she believes the finding is significant because it shows men’s brains can and do change in response to fatherhood.

“It’s super interesting because it tells us that, contrary to the narrative that men aren’t wired for care or that they aren’t designed to be caregivers, knowing that there’s adaptation and that we’re dynamic and that we can be affected by parenthood — whether we’re male or female — is meaningful regardless of the specific magnitude,” Saxbe said.

Her research found that while mothers undergo significant neurological and hormonal changes during pregnancy that prime them for caregiving, fathers tend to be “made, not born.” “When dads were spending more time with babies, they had more brain changes,” Saxbe said of her research participants.

“The more time you’re spending with your child, the more bonded you are, the more your brain is adapting,” she added. “To me, that’s a good indicator we need to be protecting dads’ time to bond. Because it’s meaningful.

The caregiving brain comes online when dads have more time with their kids.” She noted that in states that now offer paternity leave for fathers, the uptake of paternity leave has increased , meaning modern fathers are more interested in spending that time with their new addition rather than returning to work a day or a week later.

Saxbe is currently working on a seven-year follow-up study to see if the changes recorded in fathers have staying power. Research on matrescence is still nascent, but studies on the topic outnumber those on fathers and fatherhood by about 10-to-1 in peer-reviewed journals, Saxbe found.

Still, she’s sure, from her own research and interviews with different types of fathers, as well as from her own lived experience, that dads deserve to be part of this conversation. “It’s not a maternal brain and a paternal brain,” Saxbe said. “It’s a parental brain.” Carmona made a similar point, noting that hands-on experience and involvement help shape the caregiver.

“We care because we love, but we love because we care too,” said Carmona. “The more you are involved in taking care of the baby, the more you will learn and connect with that baby.” Did you use this article in your work? We’d love to hear how The 74’s reporting is helping educators, researchers, and policymakers.

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