Length of residence and pregnancy outcomes in women of migrant origin. Risks of stillbirth, infant death, caesarean section and preterm delivery

The proportion of births in Norway to foreign-born mothers is increasing. Preterm delivery, caesarean section (CS) and stillbirth is more frequent among births to several immigrant groups living in Norway. However, we know little about how these risks change with longer residency in Norway, as a proxy measure for social integration. This thesis aimed to assess the risk of adverse pregnancy outcomes among migrants living in Norway according to the length of residence and the maternal country of birth/origin. We linked nation-wide birth registration and immigration data for births during 1990-2010. In general, migrant women with long residencies in Norway did not experience a lower risk of adverse outcomes compared to migrant women with short residencies. Compared to Norwegian women, spontaneous preterm birth was more common in several minority groups and did not change with the length of residence. This was also true for emergency CSs, where the highest risk was found among Somali and Philippine women. Conversely, the risk of a planned CS was low among women from Turkey, Pakistan, Iraq, Poland and Vietnam. However, women with long residencies had a higher chance of planned CS compared to women with short residencies due to an increase in maternal wish and pregnancy complications. The risk of stillbirth and infant death, assessed in the offspring of women of Pakistani origin, were twice as high among offspring born to both first- and second-generation women compared to ethnically Norwegian women. However, mortality declined in both populations over the period. The thesis shows that length of residence does not impact equally on migrants’ pregnancy outcome. Disparities are larger between immigrant groups than between immigrants and non-immigrants. To promote equitable outcomes, targeted action is required to address high emergency CS rates as well as the prevention of maternal complications, such as diabetes, that increase with the length of time in Norway