Reproductive effort experiences, such as pregnancy, delivery, and interaction with their children, make female maternal brains optimised for child-rearing. However, extensive studies in non-human species revealed there is a trade-off between reproductive effort and life expectancy. In humans, large demographic studies have shown that this is the case for the most part, but molecular marker studies of aging remain controversial, and there are no studies evaluating the relationship between reproductive effort, aging, and brain structures simultaneously. We examined the associations among the reproductive efforts, DNA methylation age acceleration, and the regional grey matter of structural brain scans by voxel-based morphometry in 27-46-year-old mothers. We found that greater reproductive efforts, including the number of delivery and motherhood periods, were significantly associated with decelerated aging in mothers with 1-4 children. We also found that the precuneus grey matter volume was larger as age deceleration occurred and found a mediation effect of the greater left precuneus grey matter volume on the relationship between parity and age deceleration. Our findings suggest that mothers of early childhood children who have less than four children may benefit from aging via precuneus structural changes.