Neuroscientist Elseline Hoekzema and colleagues have studied brain plasticity — that is, the way the adult brain changes — for years. But it wasn’t until one of her colleagues was trying to become pregnant that the team started pondering questions of how pregnancy and motherhood change a woman’s brain.
What they found was that pregnancy reshapes the brain for at least two years afterward, with strongest effects in regions of the brain that are involved in social processing and those that respond to their child’s face. Those changes, the scientists say, may prepare a woman for the social demands of motherhood.
Previous animal studies have established that reproduction leads to long-lasting changes in brain and behavior. And scientists have long understood that hormones can change brain structure and function. But there have been few human studies. A widely reported nine-cohort study from 2002 helped create the popular idea of memory difficulties (or “momnesia”) and a general “fuzziness” in thinking as a result of having been pregnant.
Hoekzema and colleagues at the Autonomous University of Barcelona wanted to investigate how the brain physically changed in mothers. They recruited 25 first-time mothers and performed MRI brain scans both before conception and after birth, looking for pregnancy-induced structural changes in the women’s brains’ gray matter. Their brains were compared to the brains of 19 first-time fathers (scanned both before and after their partner’s pregnancy), 17 men without children, and 20 women who had never given birth.
The scientists observed that first-time mothers, but not fathers, exhibited reduced gray matter in brain regions associated with the ability to attribute thoughts, feelings, and intents to themselves or other people. But that doesn’t mean that those social capabilities were dampened — on the contrary, the researchers think the shrinkage was evidence of maturation of those social networks. Other studies have shown that pregnant women have enhanced emotion and face recognition.
Mothers with the greatest gray matter shrinkage had the highest quality of mother-to-infant attachment after birth. And a follow-up imaging session found that almost all of these brain changes lasted for nearly two years after giving birth. The study was published Monday in Nature Neuroscience.
Hoekzema and her colleagues are now working on follow-up studies based on their findings. Specifically, they want to examine how the regions of reduced brain volume are working together in the new mothers, and find out if the brain changes can predict the emergence of postpartum depression. They also want to find what happens to women’s brains after multiple pregnancies.
“This has opened up a complete new line of investigation, and I imagine we will be studying this for many years to come,” Hoekzema said.