Objectives (i) Estimate the proportion of non-registered prenatal ultrasound examinations; (ii) Examine associations between non-registered ultrasound examinations and adverse perinatal outcomes, by migrant-related factors, in women giving birth in Norway. Design A national population-based study. Setting and sample Individually linked data from the Medical Birth Registry of Norway and Statistics Norway, 1999-2016, comprising 999,760 singleton pregnancies to immigrants ( n = 196,220) and non-immigrants ( n = 803,540). Methods Crude and adjusted odds ratios (aOR) with 95% confidence intervals (CI) were estimated using logistic regression with robust standard error estimations, adjusted for year of childbirth, maternal age, parity, maternal smoking during pregnancy, educational level, and Norwegian health region at birth. Main outcome measures Prenatal ultrasound examinations; perinatal mortality; placental abruption; preeclampsia. Results Compared to non-immigrants, immigrant women had a higher proportion of non-registered ultrasound examinations (2.3% vs. 4.3% respectively). Compared to women with ultrasound examination, the aOR for perinatal mortality for women with non-registered ultrasound was 2.27 [95% CI 1.85, 2.79] for immigrants and 3.61 [3.21, 4.07] for non-immigrants. Non-registered ultrasound examination was also associated with placental abruption (aOR 1.32 [1.08, 1.63]) for non-immigrant women, but not for immigrant women. Non-registered ultrasound examination was not associated with preeclampsia in either immigrant or non-immigrant women. Conclusion Compared to non-immigrants, immigrant women have a higher proportion of non-registered data on prenatal ultrasound examinations. Both immigrants and non-immigrants with non-registered ultrasound examinations have an increased aOR of perinatal mortality, but no association was found for preeclampsia. Non-immigrant women had an increased aOR for placental abruption.

Objective To estimate the incidence of placental abruption in immigrant women compared with non-immigrants by maternal country and region of birth, reason for immigration and length of residence. Design Nationwide population-based study. Setting Data from the Medical Birth Registry of Norway and Statistics Norway (1990-2016). Sample The study sample included 1,558,174 pregnancies, in which immigrant women accounted for 245,887 pregnancies and 1,312,287 pregnancies were to non-immigrants. Methods Crude and adjusted odds ratios with 95% confidence intervals (CI) for placental abruption in immigrant women compared to non-immigrants were estimated by logistic regression with robust standard error estimations (accounting for within-mother clustering). Adjustment variables included year of birth, maternal age, parity, multiple pregnancies, chronic hypertension and level of education. Main outcome measures Placental abruption Results The incidence of placental abruption decreased during the study period for both immigrants (from 0.68% to 0.44%) and non-immigrants (from 0.80% to 0.34%). Immigrant women from the sub-Saharan African region had an adjusted odds ratio of 1.35 (95% CI: 1.15-1.58) compared to non-immigrants for placental abruption, whereas immigrant women from Ethiopia had an adjusted odds ratio of 2.39 (95% CI 1.67-3.41). We found a small variation in placental abruption incidence by other countries or regions of birth, length of residence and reason for immigration. Conclusion Immigrant women from sub-Saharan Africa, especially Ethiopia, have increased odds for placental abruption when giving birth in Norway. Reason for immigration and length of residence had little impact on the incidence of placental abruption.