Associations between non-registered ultrasound examination in pregnancy and adverse perinatal outcomes in immigrant and non-immigrant women: a Norwegian population-based study 1999–2016

Background:Prenatal ultrasound examinations are important to detect placental dysfunction. Several ultrasound-detected abnormalities can be managed during pregnancy or childbirth, thus improve health outcomes. Maternal birth country is known to influence the risk of placental dysfunction, but little is known about the possible mechanisms of this relation.Aims:(a) To estimate the proportion of non-registered prenatal ultrasound examinations; (b) to examine associations between non-registered ultrasound examinations and adverse perinatal outcomes, by migrant-related factors, in women giving birth in Norway.Methods: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). Crude and adjusted odds ratios (aORs) with 95% confidence intervals (CIs) were estimated using logistic regression with robust standard error estimations, adjusted for year of childbirth, maternal age, parity, maternal smoking, educational level and Norwegian health region at birth.Results:Compared with non-immigrants, immigrant women had a higher proportion of non-registered ultrasound examinations (2.3% vs. 4.3%; aOR 2.0 (95% CI 1.9, 2.0)). Compared with 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 it was not associated with preeclampsia.Compared with 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. Non-immigrant women also had an increased aOR for placental abruption.