Pregnancy changes the brain for as long as two years
By Amy Ellis Nutt
Dec 19 2016
For the first time, scientists have found evidence of specific and long-lasting changes in the brains of pregnant women. The changes were measured in brain areas that are responsible for social cognition and the ability to understand the thoughts and intentions of others, suggesting that they may intensify maternal bonding with a newborn.
The neuroimaging study, conducted in Spain, was prospective, looking at the brains of 25 first-time mothers before and after pregnancy, and again two years after the women gave birth. The researchers compared the brain images of these new mothers with those of 19 first-time fathers, as well as 17 men and 20 women without children. The pattern of structural changes the researchers observed in the new mothers were so distinct that it was possible to identify the mothers just from their brain scans. Those changes endured for at least two years, except for a partial return to its previous state in the hippocampus, a brain structure heavily involved with memory.
The MRI study showed changes in gray matter, the outer layer of the brain that contains the cell bodies of neurons. The gray matter in certain areas shrunk in size after pregnancy, a phenomenon known as “gray matter pruning.” A similar shrinkage is seen in early childhood and during adolescence. The gray matter contains many interconnections among neurons, and during pruning, the most important connections are strengthened and the others are left to wither. Rather than indicating a loss of ability, pruning is generally taken to mean that a brain region has become more specialized.
The researchers also found that some women had more gray matter pruning than others, and those with the most pruning seemed to bond best with their babies. “The gray matter volume changes of pregnancy significantly predicted the quality of mother-to-infant attachment and the absence of hostility toward their newborns in the postpartum period,” the authors wrote in a study published Monday in Nature Neuroscience.
In a further experiment, the researchers showed women pictures of several babies and found, unsurprisingly, that the women’s brains responded more strongly to photos of their own babies. The brain images, they said, revealed “the strongest neural activity in response to the women’s babies corresponded to regions that lost gray matter volume across pregnancy.”