The Risk of Pregnancy Associated Hypertension among Immigrants to Washington State from 2003-2013

Abstract

University of Washington Abstract The Risk of Pregnancy Associated Hypertension among Immigrants to Washington State from 2003-2013 Kristen Austin, MD Chair of the Supervisory Committee: Stephen Hawes, PhD Department of Epidemiology, Adjunct Departments of Health Services and Global Health OBJECTIVE: This study sought to determine if immigrants to Washington State had a decreased risk of pregnancy associated hypertension when compared to racially similar women born in the United States between 2003 and 2013. STUDY DESIGN: This retrospective cohort study used linked Washington State birth certificate (BC) and Comprehensive Hospital Abstract Reporting System (CHARS) data to evaluate the incidence of hypertensive disorders of pregnancy between the years 2003 - 2013. The study population consisted of the most common immigrant groups to Washington State with similar geographic area of birth: 1) North East Africa: Somalia and Ethiopia; 2) Eastern Europe: Russia and Ukraine; 3) Asia: India, Philippines, Vietnam, China and Korea; and 4) Hispanic America: Mexico. The control population consisted of United States (U.S.) born women, divided by self-identified racial subgroups (Black, White, Asian, Hispanic). The primary outcome was pregnancy associated hypertension. Confounding was evaluated by assessing risk factor variables: maternal age, pre-pregnancy BMI, weight gain during pregnancy, parity, diabetes, history of pre-existing chronic hypertension, multifetal gestations, smoking status, maternal education, paternal education, insurance type, median neighborhood income, and marital status. Multivariate regression methods assessed the association between pregnancy associated hypertension and a mother’s country of origin. RESULTS: Crude analysis confirmed that U.S. immigrants from all countries except the Philippines (OR=1.22) had lower risk of developing pregnancy associated hypertension as compared to U.S. born women of similar racial background (crude OR to develop PAH varied from 0.37 to 0.67 as compared to U.S. born women). After adjusting for the aforementioned risk factors, multivariate regression revealed that U.S. born women still have higher risk of developing pregnancy associated hypertension than U.S. immigrants born in Ethiopia, China, and Vietnam (OR =0.72, 0.51, 0.57). Immigrants born in Russia, India, Korea, and Mexico approached the same risk of developing PAH as compared to U.S. born women (OR=0.85, 0.82, 0.81, 0.84). However, the decreased risk of developing pregnancy associated hypertension in immigrant women from Ukraine (OR=0.92, CI 0.82, 1.04); and Somalia (OR=1.11, CI=0.87, 1.42) equaled the risk of U.S. born women. CONCLUSION: Country of origin is an independent risk qualifier of maternal hypertensive disorders. With the exception of Filipina women, U.S. immigrants from ethnically varied geo-political countries have lower crude risk than their U.S. born and racially similar counterparts. After multivariate adjustment, women from the Ukraine and Somalia have similar risk of pregnancy associated hypertension as U.S. born women of similar racial background. Obstetric protocols and practice management may be changed to more accurately stratify pregnancy associated hypertension risk assessment by immigrant status rather than solely on race.