Introduction
Placental abruption is a rare but serious complication affecting 3 to 10 per 1000 pregnancies worldwide (1, 2). It is a clinical diagnosis defined as partial or complete detachment of the placenta before delivery (2). The complication is associated with maternal and perinatal morbidity and mortality and accounts for around 10% of all perinatal deaths in developed countries (2). The most common risk factors include hypertension (3), pre-eclampsia (4), smoking (5) and the extremes of maternal age (1, 2). A genetic predisposition also seems to be implicated; women experiencing abruption in one pregnancy have an 11-fold increased risk of having an abruption in a subsequent pregnancy (5, 6). Abruption also occurs however, in the absence of these factors. Knowledge about additional contributing factors is important to better explain the variation of this complication in the population.
In Europe, immigrant women represent a significant proportion of all childbearing women (7) and in Norway, 29% of all births in 2019 were to immigrant women (8). Immigrants comprise a heterogeneous group, with diverse backgrounds and immigration reasons and they differ in relation to the known risk factors for placental abruption, including hypertension and smoking (9). Refugees are considered a vulnerable group for adverse pregnancy outcomes (10), while women immigrating for work or educational reasons may have equivalent or even better outcomes than the receiving population (11). Some immigrants also appear to have better health upon arrival than the host population though this may worsen over time (9).
Few studies have compared the occurrence of placental abruption between immigrant and non-immigrant women. Among those who have, an increased risk has been found for black women compared to white women (2, 12), and the risk of abruption for immigrants as a group seems to increase with length of residence in the receiving country (13). However, the analyses in these studies have not been performed according to specific maternal country or region of birth nor by reason for immigration, so potential variations in placental abruption may be masked in grouping all immigrant women together. The aims of this study were to estimate the incidence of placental abruption in immigrant women in Norway compared to non-immigrants by maternal country and region of birth, reason for immigration and length of residence.