The Brain on Pregnancy and Labor

It’s hardly a secret that both being pregnant and the act of giving birth can change not only a person’s outlook on life, but also their brain, but the question to neuroscience has always been how different, exactly. According to a recent study, however, it’s also a matter of “when.”  The authors established that the brain can look different depending on whether or not it has been examined during the pregnancy of an individual or after that person has given birth. The new research is helping to disentangle a number of the mysteries that have been ignored for a considerable period of time in the growing field of maternal neuroscience.

The study, published back in January by the journal Nature Neuroscience, followed case studies of more than one hundred new mothers over the course of several months: from the final trimester of their respective pregnancy, up until around three weeks on average after they had given birth to their baby. Past research literature had examined the birthing parents’ brain either before they had given birth or over the postpartum period, but this new study did comparisons that observed the same mothers at intervals both before and after birth. In addition, it also took into consideration whether the participants had either given a vaginal birth or had a C-section surgery. Their documented findings reveal that temporary changes occur in some regions of the brain but that there are also more permanent ones that occur in a particular brain circuit which is activated when an individual is not currently engaged in doing an active task – one that also plays a role in both self-reflection and empathizing with those around them.

As a result, this new study is said to have “ordered” a number of the ongoing scientific disagreements in the field of neuroscience, a concern addressed even by the study’s own senior author Susana Carmona, who is a neuroscience researcher at the Charles III University of Madrid in Spain.

“It fills important gaps—that is why it’s novel,” observes Joe Lonstein. Lonstein is a neuroscientist whose field interest is in animal parenting behaviors at Michigan State University but was not one of the co-authors of the new paper. “There were things we just didn’t know about the timing of events.”

We’re just beginning to scratch the surface – a phrase you often hear in the discipline of neuroscience. The bulk of scientific literature concerning pregnancy and postpartum neuroscience is just barely a decade old. One 2016 study established that the gray matter in women decreased after they had had their first baby, and that these reductions persisted on for up to six years following their pregnancy.

By contrast, some other studies have found that the volume of gray matter increases in the following weeks after people have given birth. This new paper helps to reconcile the seeming discrepancy in these results. The new study’s researchers concluded that although women did indeed lose gray matter during the course of their pregnancy and childbirth, they gained much of it back in most of their brain regions, after their child was born.

Previous studies in the literature have made observation of the changes in those parts of the brain involved with a circuit neuroscientists call the default mode network. This network is activated when an individual’s mind starts wandering or whenever they are not currently involved in performing a specific task, but the researchers have also deduced that this network is essential to one’s ability to self-reflect and also for the creation of one’s own  “internal narrative,” the way in which we build a “sense of self.”

A study from 2016 had linked these reductions in pregnancy gray-matter in this particular network to what is an increase in brain activity after the women in the study were provided with photographs of their baby crying and developing deeper parent-child attachment. Researchers also now believe that there are changes in the brain that pregnant people experience in order to prepare them not just for parenthood but simply for the act of childbirth itself—by upping their ability to tolerate pain, for one example.

Carmona’s study prioritized a focus on the brain’s default mode network and several other brain circuits and discovered that the former is in fact the only circuit that does not fully revert back to its pre pregnancy state—and that the change continues to persist for many years after the individual has given birth.

Researchers theorize that these changes that occur among birthing parents during the course of pregnancy and also following birth is a similar biological event to those changes taking place among everyone aging into their teenage years. Teenagers experience a gray matter reduction as they grow due to the numerous brain connections, or synapses, that disappear during the phase of a particular process known as “synaptic pruning.” This is hardly a bad thing. Think of it as a type of bridge lifting and closing itself as part of a typical traffic process. Carmona equates it to driving to a particular destination on a given highway with an infinite number of connecting paths. It’s easy to get to, but if you try to follow all of them, getting lost is probably inevitable. The brain goes through a period in which it closes some of those pathways, to make for easier processing of information, or streamlining.

In the way that Michelangelo’s famous statue of David was chiseled out of a block of marble, “The beauty is revealed by removing the excess,” as Emily Jacobs put it. She is a neuroscientist working at the University of California, Santa Barbara, whose field interests include the way our sex hormones shape the brain. She did not conduct research for the newly published paper.

And there is another facet that both pregnant people and teenagers share in common: considerable hormonal changes. The researchers hypothesized that the hormonal roller coaster that comes along with child birth is responsible for causing massive brain changes. In previously conducted animal studies, scientists have annexed the pregnancy hormones onto mice and documented brain changes that we often associate with maternal behavior, says Lonstein. Of course, the important caveat here is that mice are not people, and due to ethical concerns, there have not been too many experiments that test out this hypothesis on people.

This new study also concludes that women who had a vaginal birth or began going into labor but then ultimately required an emergency cesarean section took a longer span of time to “recover” from their declines in gray matter than the women who had had a normally scheduled C-section. “Going into labor triggers its own hormonal and immune cascade,” says Carmona. The researchers only used a small sample size when they conducted this portion of their study, unfortunately, so they warn that the findings in their paper need to be interpreted with a degree of caution.

One of the biggest hurdles to doing studies of this nature is simply finding the people who are willing to be test subjects. “It’s really, really hard to find women who are willing to do these things at a time in their life that can be both joyous but also very stressful,” says Lonstein.

This new study has opened a proverbial Pandora’s box of questions for researchers like Jacobs, among them: “Do nonbirthing or adoptive parents undergo similar brain changes?” or “What is the effect of labor on the birthing parent-child bond?” At the time of writing, this is a seldom explored topic of neuroscience. Among the literature there’s just half a percent of neuroscience studies that focus on topics specific to women’s health, according to another article recently authored by Jacobs, and there are numerous questions as to how pregnancy impacts changes within the brain.

Jacobs considers the fact that there have historically been few women in neuroscience may partially explain why so many of these questions weren’t addressed before. “These are women asking these questions. So it makes a pretty strong case for why diversity in science matters,” says Jacobs

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