Growing a human being is no small feat -- just ask any newly pregnant woman. Her hormones surge as her body undergoes a massive physical transformation, and the changes don't end there. A study published Monday in Nature Neuroscience reveals that during pregnancy women undergo significant brain remodeling that persists for at least two years after birth. The study also offers preliminary evidence that this remodeling may play a role in helping women transition into motherhood.

A research team at Autonomous University of Barcelona, led by neuroscientist Elseline Hoekzema of Leiden University, performed brain scans on first-time mothers before and after pregnancy and found significant gray matter changes in brain regions associated with social cognition and theory of mind -- the same regions that were activated when women looked at photos of their infants. These changes, which were still present two years after birth, predicted women's scores on a test of maternal attachment, and were so clear that a computer algorithm could use them to identify which women had been pregnant.

One of the hallmarks of pregnancy is an enormous increase in sex steroid hormones such as progesterone and estrogen, which help a woman's body prepare for carrying a child. There is only one other time when our bodies produce similarly large quantities of these hormones: puberty. Previous research has shown that during puberty these hormones cause dramatic structural and organizational changes in the brain. Throughout adolescence both boys and girls lose gray matter as the brain connections they don't need are pruned, and their brains are sculpted into their adult form. Very little research has focused on anatomical brain changes during pregnancy, however. "Most women undergo pregnancy at some point in their lives," Hoekzema says, "But we have no idea what happens in the brain."