Data sources
We used data from the Medical Birth Registry of Norway (MBRN) and
Statistics Norway during
1990-2016. In brief, the MBRN comprises mandatory, standardized
notification of all live- and stillbirths in Norway from 16 weeks of
gestation (12 weeks of gestation from 2001). It contains information on
maternal health before and during pregnancy, as well as information on
maternal and infant health during labour and birth (14). Statistics
Norway collects, processes and disseminates official statistics in
Norway (15). The data collection includes sociodemographic and migration
related factors about all individuals who are or have been resident in
Norway since 1990 (16). Data from the MBRN and Statistics Norway were
linked using the national identity
number assigned to all residents in Norway.