Rates of Preeclampsia and Post-preeclamptic Cardiovascular Disease Among US Military Servicewomen: A Retrospective Case-cohort Study
Authors: Mu Thornton S , Duran-Stanton Amelia , Stone Emily A , Zarzabal Lee Ann , Loewendorf Andrea 
Published: August 2023

ABSTRACT

Introduction
Preeclampsia (PE), a hypertensive-inflammatory disorder of pregnancy, poses acute risks of seizures, stroke, and heart attack during pregnancy and up to 6 weeks post-delivery. Recent data suggest that residual increased risks for cardiovascular disease (CVD) linger for much longer, possibly decades, after PE pregnancies. In civilian studies, PE and the major vascular events resulting from it disproportionately affect women from minority groups, especially African American women. The Military Health System (MHS) provides equal access to care for all active-duty servicewomen (ADSW), thus theoretically mitigating disparities. Racial/ethnic breakdown for PE and post PE CVD has not been studied in the MHS.

Materials and Methods
We identified healthy pregnancies in the MHS electronic health records of ADSW in the years 2009/2010 and those with a PE diagnosis. Patients with preexisting conditions of PE or CVD based on a look-back period of two calendar years were excluded. Cases were matched to controls based on age at pregnancy within 5 years and race/ethnicity. Cohort was assessed for diagnosed CVDs, race, age, and service during 2011–2017. Time to first CVD event was assessed with Cox proportional hazards model, results reported as relative risks (95% CI). All variables were summarized using mean (SD) for normally distributed continuous variables; non-normal continuous variables were characterized by median [IQR] and categorical variables were summarized by counts and frequencies. All statistical testings were two-sided with a significance level of 5% and were completed using SAS-EG version 9.2 or R version 3.5.2.

Results
From an analysis of 106,808 inpatient ADSW records, PE incidence by race is 11.8% for White, 12% for African American, 11.4% for Asian/Pacific Islander, 11.2% for Native American, 9.5% for Other, and 7.6% for unknown (not documented) race. Thus, in the US Military, African American women have comparable (0.2% higher) PE rate than White women in contrast with civilian studies that often report much higher incidence in the African American population. Using Asians as referent group, PE increases the risk of CVD. White women have a hazard ratio (HR) of 1.47 95%CI (1.15–1.88), African Americans a HR of 1.51 95% CI (1.18–1.93), and Other a HR of 1.39 95% CI (1.01–1.91).

Conclusion
In this study, we report overall higher incidence of PE in military women than what is published for civilian women in all races and across all services. Importantly, we do not find significantly higher numbers of PE and post-PE CVD for African American, compared to White women in the military. Our study is not designed to address differences between military and civilian PE epidemiology, but these results deserve further exploration. This study shines light on a health risk unique to women, which we found to be more prevalent in the US Military than published civilian population. Further study to determine the details of long-term morbidity, disability, and death attributable to PE (CVD, stroke, and kidney diseases) are needed to design optimal medical management protocols, ensure readiness for duty, and protect our Women Warfighters.