Migration-related risk factors and perinatal outcomes: A national population-based study of immigrant and non-immigrant women in Norway

Abstract

International immigration is increasing across European countries. The immigrant population is heterogeneous and comprises a high proportion of women of reproductive age. Being an immigrant woman has been associated with an increased risk of a range of adverse perinatal outcomes. With increasing immigration, enhanced and specific knowledge of immigrant women’s reproductive health, and possible risk factors for adverse perinatal outcomes, is thus considered vital. To investigate associations between maternal migration-related factors and adverse perinatal outcomes in immigrant and non-immigrant women giving birth in Norway during the study period. All papers in this thesis are based on nationwide population-based studies, comprising data from the Medical Birth Registry of Norway and Statistics Norway between 1990/1999 and 2016. In Paper I, we estimated the prevalence and odds of placental abruption in immigrant women compared to non-immigrants by maternal country of birth, reason for immigration, and length of residence using logistic regression with robust standard error estimations. In Paper II, we investigated the association between preeclampsia in the second pregnancy for women with preeclampsia in the first pregnancy, in immigrants and non-immigrants overall, and by migration-related factors, using a log-binominal regression model. In Paper III, we investigated the odds of adverse perinatal outcomes for women with non-registered ultrasound examination in pregnancy, compared to women with registered ultrasound examination, in immigrant and non-immigrant women. Associations were investigated using logistic regression with robust standard errors. Effect estimates were reported as crude and adjusted odds ratios (Paper I and III), or crude and adjusted risk ratios (Paper II), with 95% confidence intervals. We found that immigrant women from sub-Saharan Africa, especially Ethiopia, had increased odds for placental abruption compared to non-immigrant women, when giving birth in Norway. Reason for immigration and length of residence had little impact on the prevalence of placental abruption. We further found that immigrant women with preeclampsia in the first pregnancy had a substantially increased risk of preeclampsia in the second pregnancy. Being born in Latin America and the Caribbean were particularly associated with subsequent preeclampsia. Moreover, immigrant women from sub-Saharan Africa more often had missing data on prenatal ultrasound examination than non-immigrant women. We also found that women without ultrasound registered in pregnancy had an increased risk of perinatal mortality compared to women with ultrasound registered in pregnancy, in both immigrant and non-immigrant women. The risk of adverse perinatal outcomes, and the registration of prenatal ultrasound examination during pregnancy, varied by maternal country of birth. Specifically, the risk of placental abruption and non-registered ultrasound examination in pregnancy was highest for immigrant women born in the sub-Saharan African region. For women with preeclampsia in the first pregnancy, immigrant women born in Latin America and the Caribbean had the highest risk of preeclampsia in the second pregnancy. Both immigrant and non-immigrant women with non-registered ultrasound examinations in pregnancy had an increased risk of perinatal mortality than women with ultrasound registered in pregnancy. My thesis identified subgroups of immigrant women at increased risk of placental abruption, subsequent preeclampsia, non-registered ultrasound examination in pregnancy and perinatal mortality. The results highlight a need in maternity care services for tailored and intelligible information on procedures and preventive efforts to reduce adverse perinatal outcomes for immigrant women at increased risk, and the importance of ensuring complete and accurate obstetric history taking for immigrant women.