How motherhood changes the brain

In the weeks after my first son was born, I squandered hours of precious sleep leaning over his bassinet to check that he was still breathing. I researched potential dangers that seemed to grow into monstrous reality by the blue light of my smartphone. Among them: The lead paint my husband and I had discovered, a real but manageable risk, had turned our new home into a hazard zone. I cleaned our floors incessantly but still imagined a cloud of poison dust following us as I carried the baby, so tiny and fragile, from room to room.

When the doctor screened for postpartum depression during my six-week checkup, she noted that my responses to the questionnaire were somewhat mixed though my score was within the normal range. She asked whether I had thoughts about harming myself or my child, and when I said no, she moved on. But I was struggling. Before baby, I had managed a tendency toward low-level worry. Now it was as if the volume had been turned up. Among the biggest worries I faced was worry itself.

The way I saw it, motherhood made me feel this way, and I would be a mother forevermore. Would I always be this anxious? And would my baby suffer for it? I feared that something deep within me — my disposition, my way of seeing the world, myself — had been altered.

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In truth, something very foundational had changed: my brain.

What I didn't know then — what I wish I had known then — was that I was in the midst of the most rapid and dramatic neuro­biological change of my adult life. The unmooring I felt, and that so many new mothers feel, likely was at least in part a manifestation of structural and functional brain changes, handed down through the millennia by mothers past and intended to mold me into a fiercely protective, motivated caregiver, focused on my baby's survival and long-term well-being.

In the past two decades or so, researchers have begun documenting the makeover of the maternal brain. But while the transformation thought to occur is stunning, the brain remains almost entirely absent from the popular conversation about what it means to become a mother, even as a woman's body — the status of Kate Middleton's baby weight, for instance — is open to discussion ad nauseam.

Entering into motherhood is "a major event" for the brain, says Jodi Pawluski, a researcher at University of Rennes 1 in France who focuses on what she and her colleagues call the "neglected neurobiology" of the maternal brain. "It's one of the most significant biological events, I would say, you would have in your life."

Women experience a flood of hormones during pregnancy, childbirth, and breastfeeding that primes the brain for dramatic change in regions thought to make up the maternal circuit. Affected brain regions include those that enable a mother to multi­task to meet her baby's needs, help her to empathize with her infant's pain and emotions, and regulate how she responds to positive stimuli (such as baby's coo) or to perceived threats. In the newborn months, a mother's interaction with her infant serves as further stimulus to link her brain quite tangibly to her baby's.

Some effects of those brain changes may moderate over time. Researchers have found that the anxiety or hypervigilance that many new mothers feel, for example, peaks in the first month postpartum and then diminishes. But they suspect that other effects linger, shaping mothers even well past their child-rearing years and influencing their relationships with future grandchildren.

In one key study, a team of researchers used magnetic resonance imaging to look at the brains of women who were not pregnant but hoped to be. The researchers followed up with images soon after childbirth and again two years later. For comparison, they scanned women who had never had a pregnancy.

After childbirth, the volume of gray matter in the mothers' brains changed dramatically, particularly in regions involved in social processes and "theory of mind," or the ability to attribute emotions and mental states to other people — key in raising a human. The degree of change, enough that researchers could easily sort the women who had had a pregnancy from those who hadn't, surprised Elseline Hoekzema, a lead author on the 2016 paper who studies pregnancy and the brain at Leiden University in the Netherlands.

"I've never seen anything like this in any of the data sets I've worked with," Hoekzema said by email. "In a way, it's no surprise given the very extreme nature of the hormone floods that women are exposed to during this period, but still I hadn't expected such remarkably robust findings and this degree of differentiation."

The more brain change the mothers experienced, the higher they scored on measures of emotional attachment to their babies, a finding that echoed past studies. And the changes in most brain regions remained two years later.

As I read and researched, my anxiety began to feel manageable. But my frustration grew. So many women feel changed by motherhood in ways that can be unsettling and confusing. Here was information that might provide comfort to some: In most cases, not only are these changes normal, they also are productive, helping women to become the parents that their babies need. Why hadn't I known this sooner?

In those first harried weeks of new motherhood, I paged through a stack of hand-me-down parenting books while the baby slept. I was looking for something that could explain how I was feeling. In a worn copy of Infants and Mothers: Differences in Development by famed pediatrician and child development expert T. Berry Brazelton, first published in 1969, I came to a section about bringing home a newborn and read this: "Caring concern will become the foundation for learning to be a parent."

Many new mothers say that they feel like crying "most of the time" and wonder if that means they aren't cut out for being a mother, Brazelton wrote. "It must be reassuring to know that this is a common result of the physical and psychological readjustments that follow delivery. These will pass. They may even be an important part of her ability to become a different kind of ­person — a 'mother,' rather than a young girl."

I'd think about that passage often in the months to come as I dug into the research. The pregnancy tracker app that I had looked at almost daily before giving birth to see how my body was changing used an animated diagram of a woman from the neck down. Yet, half a century ago, Brazelton, who died in March, had sensed what researchers have begun to validate today using brain-imaging tools and animal models: that mothers become "a different kind of person."

Brazelton, then about to turn 98, answered his cellphone when I called in spring 2016, just as my son was turning 1. We met for lunch at the Colonial Inn, in Concord, Massachusetts. He had traveled with a caregiver from his home on Cape Cod to attend the funeral of a former colleague from Boston Children's Hospital. I told him my story, what the passage from his book had meant to me during some particularly dark days, and how it spurred my interest in the neurobiology of the maternal brain.

The anxiety I experienced was typical, he said: "You're frightened and you don't feel adequate and you're working very hard to pull yourself together, to start facing this child that you've fallen desperately in love with for the first time in your life, and you realize what a major responsibility that is and what a turning point in your life it is … I see getting disorganized and thrown into a frenzy like that as a major opportunity to reorganize yourself and pull yourself back together and become the new person that you want to be."

I felt sure he would agree with my conclusion: Shouldn't we be better informing mothers about well-documented brain changes they could expect, before baby is born?

"I don't think that most mothers are ready for that kind of information," Brazelton said. "It would scare a lot of people. I don't think they'd want to think their brains are going to change. They'd be frightened about which way it was going to go."

I fumbled with my words, dismayed and confused. The conversation had been so uplifting. Our lunch ended soon after. People were gathering at the church.

Brazelton was a progressive doctor in his day. He listened to mothers at a time when others discounted them. Yet his comments to me seemed anchored in the idea that motherhood — womanhood in general, perhaps — requires careful handling, an old idea that remains pervasive.

The truth is, it's easier to talk about decorating the nursery than about the gripping fear that sends you into a full-body sweat the first time you take baby to the grocery store. It's more comfortable to debate baby names and stroller brands than to discuss the depth of loneliness that can come at 2 a.m., when you are awake again with a crying baby.

Some of the obstacles to a more open conversation are deeply rooted — ancient, even. The belief that a woman's uterus puts her at risk for "hysteria" goes back about 4,000 years. Today, of course, the idea that her brain is muddled by motherhood fuels pregnancy discrimination in the workplace and elsewhere.

Even as we've gained a more nuanced picture of how neurology and genetics influence mental health in the population at large, researchers are playing catch-up when it comes to maternal mental health. Most parenting research is focused on the child. Researchers I interviewed said they often get a version of this response when they apply for funding to investigate the maternal brain: What about the offspring?

That's starting to change, says Dr. Samantha Meltzer-Brody, director of the perinatal psychiatry program at the University of North Carolina and president of Marcé of North America, a group that advocates for maternal mental health research, clinical care, and education. For a long time, she says, she felt like one of a few vigilantes in her field, pushing to get mothers struggling with postpartum mood disorders the support they needed.

That's no longer the case. Participation in postpartum support groups has swelled. The American College of Obstetricians and Gynecologists recently recommended redesigning postpartum care to include a fuller assessment of a woman's moods and emotional well-being. And the first drug for treating severe postpartum depression could hit the market soon.

Still, while postpartum disorders have begun getting the attention they desperately need, less time is spent helping women to understand the range of what is typical for a healthy postpartum experience and developing a new idea of motherhood that does not romanticize it. "That's where we need to go next," Meltzer-Brody says.

By the time I was expecting my second child last summer, I anticipated the emotional roller coaster of motherhood. Knowing what might be coming didn't make the ups and downs any less real, but it made them less scary. I worried plenty. But I didn't worry about the worry. I wonder how things would have been different the first time around if I'd known more. I might have coped better if I'd understood that some of what I was experiencing was just my brain — this powerful, dynamic maternal brain — doing exactly what it was supposed to do. Maybe, at the very least, it would have helped me to put down my smartphone at night and get some sleep.

Excerpted from an article that originally appeared in The Boston Globe Magazine. Reprinted with permission.