Keywords: myocardial infarction, pregnancy, risk factors, trends

Background: Cardiovascular disease is a leading cause of pregnancy-related mortality in the United States, accounting for 16.6% of maternal deaths. Acute myocardial infarction (AMI) is three to four times more likely to occur during pregnancy due to physiological hemodynamic changes. Though rare, pregnancy-associated myocardial infarction (PAMI) incidence has increased over time. Despite stable maternal mortality rates of ~4.5%, the rising incidence of PAMI highlights the need to better identify at-risk populations.

Objective: To provide an updated analysis of demographic characteristics and temporal trends of acute myocardial infarction in pregnancy amidst its rising incidence, with a secondary aim to evaluate trends in hypertensive disorders of pregnancy as a potential contributing risk factor.

Methods: Women of reproductive age hospitalized during pregnancy and the puerperium were identified from the National Inpatient Sample (NIS) database between January 1, 2018 and December 31, 2020. International Classification of Diseases, Ninth Revision (ICD-9) and Tenth Revision (ICD-10) diagnosis and procedure codes were used to identify pregnancy-related admissions, including normal and abnormal pregnancies, abortions, and deliveries. AMI and other comorbidities during these admissions was also identified using ICD-9 and ICD-10 codes.

Results: Among 11,079,833 pregnancy-related hospitalizations, 2,225 (20.1 per 100,000) involved AMI. Patients with AMI were older (32.0 vs. 29.1 years, p<0.001), more likely to be of black race (30.3% vs. 16.0%, p<0.001), and more likely to be in the lowest income quartile (37.1% vs. 28.4%, p<0.001). Comorbidities such as diabetes (4.5% vs. 1.8%), chronic hypertension (12.1% vs. 0.2%), coronary artery disease (12.8% vs. 0.0%), and heart failure (6.5% vs. 0.0%) were significantly more common (p<0.001 for all). AMI patients also had higher rates of CKD, coagulopathy, SLE, arrhythmia, and prior stroke/TIA (p<0.001). Obstetric complications including preeclampsia, eclampsia, placental abruption, postpartum hemorrhage, and postpartum infection were also significantly more prevalent among AMI cases (p<0.001).

Conclusions: The incidence of acute myocardial infarction in pregnancy has risen significantly over the past two decades and is associated with identifiable sociodemographic and clinical risk factors. These findings underscore the importance of early recognition and targeted prevention strategies. Future work will aim to develop a predictive model using machine learning to improve risk stratification and guide clinical decision-making.