Below, Susana Carmona shares five key insights from her new book, A Mother’s Brain: The New Science of the Neuro-Maternal Revolution.
Susana is a psychologist, neuroscientist, and mother. She directs the Neuromaternal Lab in Madrid, Spain, where they study how the brain changes during pregnancy, birth, and parenthood.
What’s the Big Idea?
There’s an old proverb: when a baby is born, a mother is born too. For many years, that was just a beautiful saying, but now brain data shows it contains a truth. The brain really is being deeply transformed by pregnancy and parenthood. Becoming a parent is one of life’s most profound transformations, and it deserves our curiosity, our society’s and institutions’ support, and a scientific approach.
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1. The organ that medicine forgot.
Imagine you’re in a beautiful old library. You take down one of those heavy volumes of a medical encyclopedia and open it to the section on the physiological changes of pregnancy. There’s the classic illustration: a side view of a pregnant woman’s body. Notice anything odd? Very often, that body has no head.
We might think it’s just an illustrative choice. But it reflects what we haven’t studied about pregnancy. Over the last century, we’ve mapped in exquisite detail how pregnancy remodels almost every organ: the heart, the immune system, the metabolism. That knowledge lets us catch and treat conditions like preeclampsia and gestational diabetes. But one organ was left literally out of the picture: The brain.
Research on the maternal brain is insultingly young. In 2017, we published the first study comparing women’s brains before and after they became mothers. Since then, we haven’t stopped digging into this question, and the data reveal a striking neural transformation.
We’ve discovered that the brain changes associated with pregnancy and motherhood are remarkably pronounced—as pronounced as those of adolescence, and unfolding even faster. They’re so pronounced that neuroscientists now consider peripartum one of the most plastic periods in all of adult life. Some brain regions decrease in volume during gestation and then increase after childbirth, while others follow the opposite pattern. Some return to baseline within the first years postpartum, but others persist far longer—and preliminary data suggest they may last a lifetime.
2. “Mommy brain” is not what you think.
I once saw a humorous cartoon that read: “I used to have functioning brain cells, but I traded them for children.” I think another one is much more accurate: “If you ever want to know what a mom’s brain feels like, imagine a browser with 2,897 tabs open. All. The. Time.”
Some mothers will tell you their memory and attention aren’t what they used to be. That experience is real, and dismissing it helps no one. We can joke about “mommy brain” and “momnesia,” or we can take it seriously and put a scientific lens on it. Research points to three things worth keeping in mind.
“Being a parent is like playing sudoku constantly.”
First, we have to acknowledge that gestating, giving birth, and breastfeeding are metabolically demanding—almost as much as running a marathon. Our whole body—brain included—is tired. Add to that lack of sleep. Anyone who goes through the sleep deprivation that often comes with the postpartum period is going to notice their memory and attention worsen.
Second, during postpartum, signals from the baby become the most relevant for the mother—easily hijacking her attention. A baby’s cry isn’t just another environmental stimulus. It resonates in her body, gut, and breasts. Mothers who’ve breastfed know that just hearing their baby cry can make their breasts let down milk. That’s the power of a baby’s cues. Very often, what we call forgetfulness is really this new attentional pull.
And third, caregiving carries an enormous mental load. It should be shared between both parents, but unfortunately, it still tends to fall more heavily on the mother. This is those 2,897 tabs, open all the time. A load that’s rarely named and rarely valued, but that is always there, quietly consuming resources.
All of this is most intense at the beginning. As years go by, the demands of parenting ease, and parents are left with a better-trained brain. Studies show that people who’ve been mothers or fathers actually score better, over the long term, on cognitive tests, and their brains show fewer signs of aging. Being a parent is like playing sudoku constantly.
We also learn a handful of mental skills that matter far more for our lives, personally and professionally. We learn—at lightning speed—how to care for a completely helpless being whose survival depends one hundred percent on us. We learn to regulate our emotions, plan, use our time efficiently, stay flexible when things don’t go as expected, tolerate frustration, negotiate, and work as a team—a long list of skills we should add to our CV. Someone once told me that being a parent is like earning a master’s degree in humanity, and I think he nailed it.
3. A mother carries her children’s DNA in her body for the rest of her life.
Beyond brain changes, pregnancy leaves the body another, stranger souvenir. It’s called fetomaternal microchimerism. In biology, a chimera is a single organism made of cells from two genetically distinct individuals. And that, in a small but very real sense, is what pregnancy makes of a mother. We are chimeras, formed from our own DNA and that of our children.
During gestation, the mother’s blood and the baby’s communicate through the placenta, trading oxygen, nutrients, and cells. Some cells carrying the baby’s DNA cross over and circulate in the mother. We used to think they vanished after birth. But emerging evidence suggests they don’t fully disappear. Some of these cells—or at least segments of the baby’s DNA—settle into the mother’s tissues. Researchers have found fetal DNA in mothers’ hearts, livers, lungs, and brains. This has been observed across placental mammals, including humans.
“Researchers have found fetal DNA in mothers’ hearts, livers, lungs, and brains.”
The phenomenon raises many questions. Do mothers also carry, in their tissues, the DNA of babies lost during pregnancy? Do these cells help repair tissue damaged during birth? Is this somehow connected to the higher rates of autoimmune conditions in women? The list of open questions goes on and on. Because of these findings, the phrase “a mother always carries her child in her heart” has taken on a new meaning for me.
4. Fathers’ brains change too, but differently.
In our studies, we compare women before and after pregnancy, and we also include non-gestational mothers—before and after the baby’s arrival—as well as fathers. And the results are clear: the degree of brain transformation a mother goes through during pregnancy is much, much more marked than what a father or a non-gestational mother experiences. Pregnancy is, first and foremost, an extraordinary physiological event that demands profound biological adaptations in practically every organ of a woman’s body, the brain included.
Some of those brain adaptations facilitate the mother’s well-being and her bond with the baby. Does that mean only biological mothers know how to care for their children? No. We cannot equate a brain change with maternal behavior. Our data show that some of these brain changes facilitate the bond with the baby, but they don’t determine it. Brain changes are neither necessary nor sufficient for bonding. Non-gestational caregivers—fathers, adoptive mothers, grandmothers—are, obviously, wonderful caregivers. I don’t think you need a brain scan to make that case, but if you did, we have that too: the brains and hormone levels of non-gestational parents also adapt, just by a different route and with a different magnitude and timing.
In mothers, two forces act at once: gestation, and contact with the baby. In fathers, and in non-gestational caregivers, it’s mostly the second. Every bath, every time you get up in the middle of the night to calm the baby, every nap together, every feed fine-tunes the bond and the caregiving. What really seems necessary to bond deeply with a baby is the time you spend with them. We care because we love, but we also love because we care.
5. A more plastic brain is also more vulnerable.
A plastic brain is also a vulnerable brain. A brain changing this fast and this deeply is also more sensitive to what surrounds it, more open to harm. Picture the brain as a piece of clay. The hormones of pregnancy and birth are water that softens the clay, and caring for the baby is the pressure of the fingers that shape it. But that same softness that lets the clay take a new form is also what can crack it. In that extremely malleable state, the piece is also very exposed. It can be shaped, too, by a traumatic birth, by sleep deprivation, by a lack of social support, by financial stress, by maternity leave that’s far too short, and so on.
“Roughly one in five women experiences perinatal depression.”
In the society we live in, perinatal mental health problems are very common. Roughly one in five women experiences perinatal depression. In wealthy countries, suicide linked to peripartum mental disorders is one of the leading causes of maternal death. This, of course, doesn’t affect only the mother. It reverberates to the baby, the family, and our whole society.
In the last few years, we’ve made great advances in treatment, but there’s still a long way to go, especially in prevention. That road has to start by describing, in detail, what actually happens in a mother’s brain during pregnancy and the postpartum period, and by characterizing how those changes are shaped not only by biology but by society and policy too.
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