Pregnancy leads to structural changes in the brain that persist for at least two years, according to a study of 25 first-time mothers published online this week in Nature Neuroscience. These changes occur in regions that are involved in social cognition and that respond to images of the mother’s infant. Furthermore, the extent of the changes can predict a mother’s attachment to her child.
Pregnancy is accompanied by drastic physiological and physical changes in the body due to extreme surges of hormones. Although we know that less radical hormonal changes - such as those seen during puberty - can modulate human brain structure and function, the structural changes within a mother’s brain as a result of pregnancy have yet to be determined.
Elseline Hoekzema and colleagues designed a prospective study that examined 25 first-time mothers both before and after pregnancy to characterize pregnancy-induced structural changes in their brains’ gray matter. Compared to the brains of 19 first-time fathers, 17 men without children and 20 women who had never given birth, first-time mothers exhibited reduced gray matter in regions associated with theory of mind, or the ability to attribute mental states such as thoughts, feelings and intents to themselves or other people. This pattern of structural changes could be used to distinguish the brains of women who had eventually given birth from those who did not, as well as predict the quality of mothers’ attachment to their infants in the postpartum period. The authors observed increased neural activity in some of these pregnancy-modified brain regions when they showed mothers pictures of their own infants, relative to images of other babies. Finally, a follow-up imaging session determined that almost all of these gray-matter reductions were maintained in the first-time mothers nearly two years after giving birth, except for a partial recovery of gray-matter volume in the hippocampus, a region associated with memory.
This study provides the first glimpses into the extensive changes in brain structure and function that result from first-time pregnancy. The authors suggest that these changes may prepare a woman for the social demands of imminent motherhood.