‘Mommy brain’ doesn’t capture how the brain transforms during pregnancy

Pregnancy shrinks parts of the brain. That sounds bad. Throw in the forgetfulness and fogginess, or “momnesia,” that many moms report, and what’s left is the notion that for the brain, the transition to motherhood is a net loss.

“I see it on social media all the time,” says neuroscientist and therapist Jodi Pawluski of the University of Rennes in France. “Your brain shrunk. This is why [you] forget everything.”

But that’s just not true, Pawluski says. The perception that the maternal brain is dysfunctional has gone on long enough: It’s time to “start giving the maternal brain the credit it deserves,” Pawluski and her colleagues write February 6 in in JAMA Neurology.

Pregnancy does kick-start structural changes in the brain, including a loss of gray matter. But the loss isn’t automatically a bad thing — reductions can reflect a fine-tuning process that makes the brain more efficient (SN: 3/18/22).

During the transition to motherhood, the brain reorganizes its connections, strengthening those that are useful and letting go of those that aren’t, Pawluski says. This reorganization prepares the brain “to learn rapidly to keep a baby alive,” she says.

In a 2016 study, for example, researchers reported brain changes, including reductions, that appear to foster attachment to a new baby (SN: 12/19/16). Other work by this team found pregnancy-triggered decreases in the volume of the ventral striatum, a region involved in motivation and reward. Those reductions in mothers’ brains were associated with a heightened responsiveness toward their babies, the team reported in Psychoneuroendocrinology in 2020.

Still, many pregnant and postpartum women do report memory loss. Studies haven’t found large differences when testing memory for new moms compared with nonmothers, Pawluski says, but more research is needed to understand the mental load of parenthood — the impact of endless tasks and distractions.

A possible explanation for “momnesia” or “mommy brain” is that new mothers turn their attention toward baby and away from other things. Indeed, pregnant women, in contrast to never-pregnant women, demonstrated a boost in learning about baby-related objects as compared with adult-related items, researchers reported in Memory in 2022. Pregnant women also fared better with recalling relationships between objects and locations.

The changes in the maternal brain are akin to those seen during adolescence. A study of first-time mothers and female adolescents found that the reductions in volume in the maternal brain matched those seen in the teens, researchers reported in Human Brain Mapping in 2019. “We accept adolescence as being a time of transition and a lot of neuroplasticity,” or the brain’s ability to change, Pawluski says. The shift to motherhood is just as impactful on the brain, she says.

Giving the maternal brain its due for its incredible adaptations does not mean that caregiving is a skill exclusive to those who give birth. While hormones trigger brain modifications during pregnancy, nonbirthing parents’ brains change with the experience of having a newborn. After the birth of their first child, new fathers’ brains showed a reduction in gray matter, but childless men’s brains didn’t, researchers reported in Cerebral Cortex in 2022.

Changing misperceptions about the brain during the transition to motherhood “comes back to acknowledging the importance of caregiving,” Pawluski says, by all parents. “The ability for your brain to actually learn to keep a baby alive is a big deal.”