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  • "That’s the maternal motive or instinct—a core, pro-baby drive that overrides the other stuff of life." Tweet This
  • "The neuroscience squares with what many moms sense in the delivery room, via the surreal experience of meeting a stranger who you somehow already love passionately. You aren’t quite in your right mind, and yet this new mind isn’t wrong." Tweet This
Category: Parents, Interview

We live in a culture that tends to frame childbearing through the lens of loss: a loss of self, sleep, personal space, or brain capacity. A momentary weakness to be overcome as quickly as possible. On the other hand, researchers have noted the disparities between prenatal care and the dearth of understanding regarding the many incredible changes that take place pre/postpartum in a woman’s mind, body, and spirit. Those changes are the subject of a new book by New York Times bestselling author, Abigail Tucker: Mom Genes: Inside the New Science of Our Ancient Maternal Instinct.

Drawing from hard scientific research as well as her own experience as the mother of four thriving children, Mom Genes presents a heartfelt and engaging “Momior” just in time for the celebration of Mother’s Day. I recently had the opportunity to discuss Mom Genes with Tucker, who provides more insights from her research on the “making of a mother.”

Emma Posey: In your book, you discuss the varied biological and neurological changes women undergo in pregnancy and childbirth, and you reflect on the idea that “the most important change in motherhood isn’t about how we look on the outside. It’s about how we see.” How has your perspective changed since becoming a mother, and what are the major differences that occurred that surprised you? 

Abigail Tucker: Moms know in our marrow that we are different from our previous selves. In addition to the extremely weird, outwardly obvious stuff that happens to the rest of our bodies— gaining 60 pounds, for starters, or growing hair that is suddenly curly—we undergo a very startling brain change. Whether or not the brain is the most important organ during childbirth, it’s one of the most altered afterward.

If you take scans of women’s brains before and after pregnancy, there are measurable differences that apparently persist for years. Scientists aren’t completely sure what all the differences mean, but they know mom brains are sensitized in dramatic ways. We react differently when shown baby pictures. We respond more quickly to infant cues. We have a new relationship to our environment—to smells, to threats, to stranger’s faces. 

While pregnant with my fourth child, I volunteered for an experiment where I wore an EEG cap and looked at baby pictures while scientists recorded the electrical readings from my scalp. Those readings would, on average, be different from childless people’s, and even from my husband’s. If you put me in an fMRI scanner, I would likely be using slightly different brain parts than a non-mom to process infant screams. 

But as one researcher told me, we don’t need neuroimaging to tell us this. The neuroscience squares with what many moms sense in the delivery room, via the surreal experience of meeting a stranger who you somehow already love passionately. You aren’t quite in your right mind, and yet this new mind isn’t wrong. 

Posey: You also dispute common myths about what the “maternal instinct” is based on your research and lived experience. What is/isn’t maternal instinct based on your findings?

Tucker: It’s common to hear people who have not yet had children say, “I don’t have a maternal instinct.” That’s because it’s not something you are born with—or you could say that you’re born with the seeds of the instinct, but it doesn’t come to life unless something happens to make it grow.

Motherhood, in this sense, isn’t an impulse; it’s a stage of human development, one that you enter when you become pregnant and give birth, and you become highly sensitized to and motivated by infant cues, with your brain getting rewired accordingly. 

But it the full change doesn’t just happen automatically: Along with oxytocin and other hormones that are released in pregnancy and childbirth, the hands-on encounter with the baby is important. That’s why adoptive mothers can experience their own version of the maternal transformation once they develop a strong relationship with the child. And for biological mothers, once the mother-child relationship is established, it persists independent of birth hormones, which are ultimately flushed from our system. 

It’s important to note that the emergence of a maternal instinct is not about suddenly uploading a childcare encyclopedia into your brain. It’s not about knowing how to do stuff like change a diaper or mix formula. It’s about wanting to know what to do to care for your kid and never stopping until you figure it out. The maternal instinct is above all a shift in motive—a transformation, a kindling, an unmasking of a new self. And again, it’s an embodied change, not just a made-up story we tell ourselves.

You can watch this play out in a lab. Lab rats who are not yet mothers are motivated by food, especially junk food like Charleston Chews and Froot Loops. But after they give birth, female rats choose babies over food, and even babies over cocaine. The rat moms will cross an electric grid to get babies. They will bury themselves in a baby avalanche if you let them. These are desires familiar to human new mothers like me, who simply couldn’t fathom the baby thing before giving birth, but who are afterward somewhat obsessed. That’s the maternal motive or instinct for you. It’s a core, pro-baby drive that overrides the other stuff of life.

Motherhood, in this sense, isn’t an impulse; it’s a stage of human development, one that you enter when you become pregnant and give birth [where] you become highly sensitized to and motivated by infant cues, with your brain getting rewired accordingly. 

PoseyI found your discussion on “gray matter” in women’s brains pre/postpartum very interesting as it presents researchers with literal examples of women’s brains changing through pregnancy and childbirth. Can you explain more about that, and what changing levels of gray matter in a Mom’s brain tells us?

Tucker: Gray matter is the information processing parts of our brains. Researchers take scans of women before they get pregnant, during pregnancy and afterward, and record changes in brain volume. One lab in the Netherlands, led by neuroscientist Elseline Hoekzema of Leiden University, recently published some very interesting findings: they reported that women’s brains shrank in areas that neuroscientists think are related to processing and responding to social signals, and that these changes lasted for at least two years. Furthermore, they found that individual women had different degrees of shrinkage, and that those who experienced the greatest degree of brain shrinkage had the strongest attachment to their kids.

Importantly, neuroscientists assure us that brain shrinkage is not the same thing as atrophy—it could be what researchers call neural pruning or refinement, with the brain getting leaner and meaner and more efficient in some way. Furthermore, these are very early days for this kind of research, and other labs have found increased brain volume in similar areas. (This variation is likely because different labs have different ways of measuring the brain.) But the scientists agree that tangible change occurs, and that the change is likely not the same for every mom. 

PoseyI am in the process of completing a research project on noncustodial fathers. One of the main findings from my study was that fathers who spent time with their children as the primary caregiver and encountered the child’s need/vulnerability experienced a “light bulb” moment of recognition regarding their role as a father, which led to subsequently higher levels of child support payments. You present similar findings in your book where you write, “But whatever the mechanism, a key difference between biological moms and dads is this: new moms are hormonally primed to seek out experience with infants, while new dads must have those experiences in order to get their hormones rolling.” Can you discuss the biological/neurological role of the father in the “making of the mother” and the “making of the child”?

Tucker: Well, dads definitely contribute to the “making of the mother” by kickstarting the process of conception and pregnancy, and placental hormones like estrogen and progesterone…stimulate maternal care. It seems that mom and dad’s genes have slightly different roles in creating the placenta, with the dad’s genes effectively pushing behind the scenes for a bigger, stronger placenta, stripping nutrition from the mom to provision the baby, and flooding her body with chemicals to maximize maternal care after the baby is born. Meanwhile, the mom’s body is trying to conserve her own resources. 

As for the way dads themselves transform, they can undergo hormonal changes like drops in testosterone during their partners’ pregnancy, though to a less striking degree than what pregnant women experience. But they have to make the effort to be physically present with their partners and their children in order to go through a paternal transformation. If a man gets a woman pregnant and never sees her again or meets his child, the man is not going to transform into a father. The woman, however, will become a mom regardless of her relationship with her partner. But dads’ brains can and do change if they put in the hours. That “aha” moment really can happen, and the magic ingredient is time. Taking paternity leave, for instance, and pitching in during those early days may be the best way to begin.

Meanwhile, dads are still essential to the making of mothers after the baby is born, in that a supportive paternal presence can promote maternal mental health. Consider the problem of intergenerational abuse. Maternal behaviors seem to run in families, repeating over and over in cycles that can be very hard to break. A supportive relationship with a romantic partner can help a new mom snap out of the cycle. Paternal presence can enhance maternal behavior by reducing maternal stress levels. This may be why one study of a Swedish paternity leave policy showed that paid paternal leave correlates with a drop in the number of anti-anxiety medications that new mothers take. 

Posey: Mom Genes discussed a few biological findings regarding mothers that literally caused my jaw to drop. One of these moments occurred after reading about “fetal microchimerism.” Conversations around motherhood typically focus on what the mother gives or loses for the sake of the child, but this is poignant example of something the unborn child gives to the mother. Can you tell us more about it? 

Tucker: In pregnancy, small numbers of fetal cells pass through the placenta into the body of the mother. Some of them stay there inside her forever, integrating into the tissue of her various organs, from liver to brain. This is called “fetal microchimerism.” Some researchers think these cells help heal mother’s bodies–there’s a famous story about a woman whose diseased liver was found to have been rebuilt by the cells of a son she never had. (She’d had an abortion, but the fetus in one sense lived on inside her.) There is evidence that the fetal cells help regenerate mothers’ heart tissue after heart attacks, and I visited a lab where scientists are exploring how these cells might be used in therapies for non-mothers and men, too. It seems logical that the fetus would protect the mother, who is so important to the baby’s survival. 

Of course, the story is likely not that simple. Other scientists have proposed that the fetal cells are effectively looking out for the fetus’s interests—increasing a mom’s milk output, for instance. But whatever the truth may be, I see fetal microchimerism as further proof that moms are different from other people—not better or worse, but unique in ways that are worth trying to understand. Few labs are currently studying this, even though 90 percent of the women in the world are mothers. Yet there’s so much at stake here for all of us.  

Emma Posey is a Coalitions and Personnel Manager at American Moment and a research assistant to W. Bradford Wilcox.