How motherhood changes the brain
Pregnancy and childbirth set off some of the starkest biological alterations a woman’s brain undergoes, said Chelsea Conaboy. So how come no one tells you about them?
I N 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. 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 transfor- mation 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 e-mail. “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