Background: Severe maternal morbidity (SMM) is broadly defined as an unexpected and potentially life-threatening event associated with labor and delivery. The Centers for Disease Control and Prevention (CDC) produced 21 different indicators based on International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) hospital diagnostic and procedure codes to identify cases of SMM. Objectives: To examine existing SMM indicators and determine which indicators identified the most in-hospital mortality at delivery hospitalization. Methods: Data from the 1993-2015 and 2017-2019 Healthcare Cost and Utilization Project's National Inpatient Sample were used to report SMM indicator-specific prevalences, in-hospital mortality rates, and population attributable fractions (PAF) of mortality. We hierarchically ranked indicators by their overall PAF of in-hospital mortality. Predictive modeling determined if SMM prevalence remained comparable after transition to ICD-10-CM coding. Results: The study population consisted of 18,198,934 hospitalizations representing 87,864,173 US delivery hospitalizations. The 15 top ranked indicators identified 80% of in-hospital mortality; the proportion identified by the remaining indicators was negligible (2%). The top 15 indicators were: restoration of cardiac rhythm; cardiac arrest; mechanical ventilation; tracheostomy; amniotic fluid embolism; aneurysm; acute respiratory distress syndrome; acute myocardial infarction; shock; thromboembolism, pulmonary embolism; cerebrovascular disorders; sepsis; both DIC and blood transfusion; acute renal failure; and hysterectomy. The overall prevalence of the top 15 ranked SMM indicators (~22,000 SMM cases per year) was comparable after transition to ICD-10-CM coding. Conclusions: We determined the 15 indicators that identified the most in-hospital mortality at delivery hospitalization in the US. Continued testing of SMM indicators can improve measurement and surveillance of the most severe maternal complications at the population level.

The authors have declared no competing interest.

This study did not receive any funding.

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The data underlying the results presented in the study are public use and available for purchase from the Healthcare Cost and Utilization Project (HCUP) - National (Nationwide) Inpatient Sample (NIS) via their website https://www.hcupus.ahrq.gov/nisoverview.jsp. All interested researchers can access the data through HCUP directly. We are not permitted to share the data or make it available as per the data use agreement with HCUP. The data use agreement required of all users is located here: https://hcup-us.ahrq.gov/team/NationwideDUA.jsp. The authors did not have any special access privileges to these data.

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I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

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The data underlying the results presented in the study are public use and available for purchase from the Healthcare Cost and Utilization Project (HCUP) - National (Nationwide) Inpatient Sample (NIS) via their website https://www.hcupus.ahrq.gov/nisoverview.jsp. All interested researchers can access the data through HCUP directly. We are not permitted to share the data or make it available as per the data use agreement with HCUP. The data use agreement required of all users is located here: https://hcup-us.ahrq.gov/team/NationwideDUA.jsp. The authors did not have any special access privileges to these data.

https://www.hcupus.ahrq.gov/nisoverview.jsp