Migration related factors
The Global Burden of Diseases (GBD) study represents a major
international effort that quantifies levels and trends in health to
allow for comparison of the magnitude of different risk factors and
health outcomes in the world (17). We analysed data by maternal region
of birth using the seven super regions defined by the GBD: (i) Central
Europe, Eastern Europe and Central Asia; (ii) High-income; (iii) Latin
America and Caribbean; (iv) North Africa and Middle East; (v) South
Asia; (vi) Southeast Asia, East Asia and Oceania; (vii) Sub-Saharan
Africa.
Separate analyses by maternal country of birth were also performed for
all countries with more than 6000 registered pregnancies (14 countries)
or more than 15 registered placental abruptions (an additional 11
countries) during the study period. Immigrant women from countries with
fewer abruptions or pregnancies were grouped and coded as other
countries . Reason for immigration included: education, family
reunion/establishment, refugee, work, unspecified/other (8). Women from
the Nordic countries (Denmark, Sweden, Finland and Iceland) are
permitted to move freely across the Nordic countries and were included
as a separate category (Nordic immigrants ). Maternal length of
residence was categorized as <1 year, 1-4 years, ≥ 5 years and
was calculated as the difference between the year of birth and the year
of official residence permit.