Preeclampsia by maternal reasons for immigration: a population-based study

Background: To investigate whether the occurrence of preeclampsia varied by maternal reasons for immigration. Methods: We included 1,287,270 singleton pregnancies (163,508 to immigrant women) in Norway during 1990-2013. Individual data were obtained through record linkage between the Medical Birth Registry of Norway and Statistics Norway. Analyses were performed for preeclampsia overall and in combination with preterm birth < 37 and < 34 weeks of gestation, referred to as preterm and very preterm preeclampsia. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated using logistic regression with robust standard errors, adjusted for relevant covariates, including maternal income and education. Results: Preeclampsia was reported in 3.5% of Norwegian women and 2.5% of immigrants. Compared with Norwegian women, the adjusted OR for preeclampsia was lowest in labour immigrants (adjusted OR 0.55 [95% CI 0.49-0.62]), followed by family immigrants (0.62 [0.59-0.65]), immigrant students (0.75 [0.65-0.86]), refugees (0.81 [0.75-0.88]), and immigrants from other Nordic countries (0.87 [0.80-0.94]). Compared with Norwegian women, labour immigrants also had lower adjusted odds of preterm and very preterm preeclampsia, whereas refugees had increased adjusted odds of preterm and very preterm preeclampsia (< 37 weeks: 1.18 [1.02-1.36], and < 34 weeks: 1.41 [1.15-1.72]). Conclusions: The occurrence of preeclampsia was lower overall in immigrants than in non-immigrants, but associations varied by maternal reasons for immigration. Maternity caregivers should pay increased attention to pregnant women with refugee backgrounds due to their excess odds of preterm preeclampsia.