Hospital Discharge Codes and Overestimating Severe Maternal Morbidity During Delivery Hospitalization.

Our objective was to identify birth hospitalization severe maternal morbidity (SMM) diagnoses that were also coded during prior encounters and, thus, potentially falsely carried forward as de novo SMM events. This retrospective cohort study included pregnant patients with births between 2016 and 2020. We applied the SMM algorithm to the birth hospitalization and encounters occurring prepregnancy, antepartum, and postpartum. The primary outcome was the rate of SMM diagnoses recorded during the birth hospitalization that were also coded on previous encounters. There were 1,380 (1.8%) birthing patients with SMM. Of patients with SMM codes at the birth hospitalization, 19.0% had the same SMM code during a prior encounter. Certain SMM events may be prone to carry-forward errors and may not signify a de novo birth hospitalization event.