Objective To investigate national trends of SBS diagnosis codes and how trends varied among patient and hospital characteristics. Methods We examined possible SBS, confirmed SBS, total SBS, and non-SBS abuse diagnoses among children age three and younger who were hospitalized for abuse between 1998 and 2014 using a secondary analysis of the National Inpatient Sample, the largest US all-payer inpatient care database (N = 66,854). A baseline category logit model was used based on a quasi-likelihood approach (QIC) with an independent working correlation structure. Results The rate (per 100,000 census population) of total SBS diagnoses was 5.4 (± 0.3) between 1998 and 2014, whereas the rate of non-SBS abuse was 19.6 (± 1.0).The rate of confirmed SBS diagnoses increased from 3.8 (± 0.3) in 1998 to 5.1 (± 0.9) in 2005, and decreased to 1.3 (± 0.2) in 2014. Possible SBS diagnoses were 0.6 (± 0.2) in 1998, increasing to 2.4 (± 0.4) in 2014. Confirmed SBS diagnoses have declined since 2002, while possible SBS diagnoses have increased. All abuse types were more frequent among infants, males, children from low-income homes, and urban teaching hospitals. Conclusions We investigated seventeen-year trends of SBS diagnoses among young children hospitalized for abuse. The discrepancy between trends in possible and confirmed SBS suggests differences in norms for diagnosing SBS, which has implications for which cases are considered AHT. Future research should investigate diagnostic processes for SBS and whether all codes associated with abusive head injuries in young children are classified as AHT. Our findings also highlight the relativity defining and diagnosing SBS. Medical professionals find utility in diagnosing SBS, though may be more apt to apply possible SBS diagnoses to abusive head injuries in children. Clarifying norms for SBS diagnosis and refining definitions for AHT will ensure that young children presenting with abusive head injuries are included in overall counts of AHT. This baseline data, an essential component of child abuse surveillance, will enable ongoing efforts to track, prevent, and reduce child abuse.