Trends in Severe Maternal Morbidity in the US Across the Transition to ICD-10-CM/PCS From 2012-2019

IMPORTANCE: Surveillance of severe maternal morbidity (SMM) is critical for monitoring maternal health and evaluating clinical quality improvement efforts. OBJECTIVE: To evaluate national and state trends in SMM rates from 2012 to 2019 and potential disruptions associated with the transition to International Classification of Diseases, 10th Revision, Clinical Modification and Procedure Coding System (ICD-10-CM/PCS) in October 2015. DESIGN, SETTING, AND PARTICIPANTS: This repeated cross-sectional analysis examined delivery hospitalizations from 2012 through 2019 in the Healthcare Cost and Utilization Project’s National Inpatient Sample and State Inpatient Databases, an all-payer compendium of hospital discharge records from community, nonrehabilitation hospitals. Trends were evaluated using segmented linear binomial regression models that allowed for discontinuities across the ICD-10-CM/PCS transition. Analyses were completed from April 2021 through March 2022. EXPOSURES: Time, ICD-10-CM/PCS coding system, and state. MAIN OUTCOMES AND MEASURES: SMM rates, excluding blood transfusion, per 10 000 delivery hospitalizations, overall and by indicator. RESULTS: From 2012 to 2019, there were 5 964 315 delivery hospitalizations in the national sample representing a weighted total of 29.8 million deliveries with a mean (SD) maternal age of 28.6 (5.9) years. SMM rates increased from 69.5 per 10 000 in 2012 to 79.7 per 10 000 in 2019 (rate difference [RD], 10.2; 95% CI, 5.8 to 14.6) without a significant change across the ICD-10-CM/PCS transition (RD, −3.2; 95% CI, −6.9 to 0.6). Of 20 SMM indicators, rates for 10 indicators significantly increased while 3 significantly decreased; 5 of these changes were associated with ICD-10-CM/PCS transition. Acute kidney failure had the largest increase, from 6.4 to 15.3 per 10 000 delivery hospitalizations (RD, 8.9; 95% CI, 7.5 to 10.3) with no change associated with ICD transition (RD, −0.1; 95% CI, −1.2 to 1.1). Disseminated intravascular coagulation had the largest decrease from 31.3 to 21.2 per 10 000 (RD, 10.2; 95% CI, −12.8 to −7.5), with a significant drop associated with ICD transition (RD, −7.9; 95% CI, −10.2 to −5.6). State SMM rates significantly decreased for 1 state and significantly increased for 21 states from 2012 to 2019 and associations with ICD transition varied. CONCLUSIONS AND RELEVANCE: In this cross-sectional study, overall US SMM rates increased from 2012 to 2019, which was not associated with the ICD-10-CM/PCS transition. However, data for certain indicators and states may not be comparable across coding systems; efforts are needed to understand SMM increases and state variation.