Pregnancy is associated with a surge of sex hormones akin to the heightened production of sex hormones during puberty. The researchers noted that gray matter also is pruned during adolescence, when a spectrum of emotional, cognitive and behavioral neural changes begin to fine tune the teenage brain.

Cordelia Fine, a psychologist at the University of Melbourne who had no part in this research, said that “this is a solid study,” despite the small sample size. Fine has written several books about gender and how male-female differences are often overstated in science. “The authors are appropriately careful not to conclude that the brain changes they observe are caused by hormones (or by hormones alone), since they don’t show this directly. However, this is certainly a plausible hypothesis.”

Fine cautions that the brain areas identified by the scientists are also responsible for other functions, not simply attachment. A more significant caveat, she said, is that while the authors of the study “speculate that the structural brain changes they see underlie maturation” of neural networks that “could facilitate attachment . . . it’s worth noting that the authors measured empathy before and after pregnancy, and found no change.”
According to the authors of the study, these brain changes may “serve an adaptive purpose for pending motherhood,” that is, the stronger the mother-child attachment, the greater chance the child survives.