Hypertension in Pregnancy Among Immigrant and Swedish Women: A Cohort Study of All Pregnant Women in Sweden

BACKGROUND: Little is known about risks of hypertensive disorders of pregnancy in both first- and second-generation immigrant women in Europe and other Western countries; such knowledge may help elucidate the influence of genetic versus social factors on such risks. We aimed to study both first- and second-generation immigrant women for the presence of all types of hypertension (preexisting hypertension, gestational hypertension, preeclampsia, and eclampsia) during pregnancy. METHODS AND RESULTS: A cohort study was conducted using data derived from the Swedish National Birth Register, the National Patient Register, and the Total Population Register. We used Cox regression analysis to compute hazard ratios (HRs) and 99% CIs while adjusting for sociodemographic factors and comorbidities. The first-generation study included a total of 1084212 deliveries and 68311 hypertension cases, and the second-generation study included 989986 deliveries and 67505 hypertension cases. The fully adjusted HR (with 99% CI) for hypertension in pregnancy among first-generation immigrant women was 0.69 (0.66-0.72), and among second-generation immigrant women, it was 0.88 (0.86-0.91), compared with Swedish-born women with 2 Swedish-born parents. Women born in Finland or with parent(s) from Finland had higher risks, with fully adjusted HRs (99% CIs) of 1.30 (1.18-1.43) and 1.12 (1.07-1.17), respectively. CONCLUSIONS: Both first- and second-generation immigrant women had overall lower risks of hypertension in pregnancy compared with other Swedish women. However, the risk reduction was less pronounced in second-generation compared with first-generation immigrant women, suggesting that environmental factors in Sweden may have an important influence on risk of hypertension during pregnancy.