Mapping the impact of pregnancy on the human brain is essential for understanding the neurobiol-ogy of maternal caregiving. Recently, we found that pregnancy leads to a long-lasting reduction incerebral gray matter volume. However, the morphometric features behind the volumetric reductionsremain unexplored. Furthermore, the similarity between these reductions and those occurring duringadolescence, another hormonally similar transitional period of life, still needs to be investigated.Here, we used surface-based methods to analyze the longitudinal magnetic resonance imaging dataof a group of 25 first-time mothers (before and after pregnancy) and compare them to those of agroup of 25 female adolescents (during 2 years of pubertal development). For both first-timemothers and adolescent girls, a monthlyrate of volumetric reductions of 0.09 mm3was observed. Inboth cases, these reductions were accompanied by decreases in cortical thickness, surface area, localgyrification index, sulcal depth, and sulcal length, as well as increases in sulcal width. In fact, the changesassociatedwithpregnancydidnotdifferfrom those that characterize the transition duringadolescence in any of these measures. Our findings are consistent with the notion that the brainmorphometric changes associated with pregnancy andadolescence reflect similar hormonally primedbiological processes.