The purpose of this study was to evaluate narrower age groups in children aged 0–4 years to determine whether guidelines should be refined when investigating femur fractures for nonaccidental trauma (NAT). This was a retrospective review of the pediatric trauma database at our level 1 pediatric trauma center. The database was examined from 2009 to present. We examined rates of NAT in the less than or equal to 12-month, 13–24-month, 25–36-month, and 37–48-month age groups. χ2 was used to compare rates of NAT between these groups, and P less than 0.05 was considered to be significant. Over the indicated time period, there were 138 femur fractures in children aged 0–4 years, of which 30 were determined to be NAT. The rate of NAT in the less than or equal to 12-month age group was 74.1%, accounting for 20 of the 30 NAT femur fractures. A significant difference in rates of NAT was found between the less than or equal to 12-month age group and all other age groups (P<0.00001). No significant difference in rates of NAT was found between the 13–24-month, 25–36-month, and 37–48-month age groups. Although our institution has generally felt that NAT should be universally evaluated in patients below 36 months of age with femur fractures, our data suggest that there is little justification for universally evaluating 13–36-month-old patients with femur fractures for NAT when the rates do not differ for 37–48-month-old patients. NAT does exist in femur fractures in children above 12 months of age, but it is most worrisomely high in patients of less than or equal to 12 months of age.