Perinatal mortality among pregnant undocumented migrants in Norway 1999-2020: A register-based population study.

Background: Irregular legal status is a recognized health risk factor in the context of migration. However, undocumented migrants are rarely included in health surveys and register studies. Adverse perinatal outcomes are especially important because they have long-term consequences and societal risk factors are modifiable. In this study, we compare perinatal outcomes in undocumented migrants to foreign-born and Norwegian-born residents, using a population-based register.
Methods: We included women 18-49 years old giving birth to singletons as registered in the Medical Birth Registry of Norway from 1999 to 2020. Women were categorized as 'undocumented migrants' (without an identity number), 'documented migrants' (with an identity number and born abroad), and 'non-migrants' (with an identity number and born in Norway). The main outcome was perinatal mortality, i.e., death of a foetus ≥ gestational week 22, or neonate up to seven days after birth. We used log-binominal regression to estimate the association between legal status and perinatal mortality, adjusting for several maternal pre-gestational and gestational factors. Direct standardization was used to adjust for maternal region of origin.
Ethical Approval: Regional Ethical Committee (REK South East, case number 68329).
Results: We retrieved information on 5856 undocumented migrant women who gave birth during the study period representing 0.5% of the 1 247 537 births in Norway. Undocumented migrants had a relative risk of 6.17 (95% confidence interval 5.29 ̶7.20) of perinatal mortality compared to non-migrants and a relative risk of 4.17 (95% confidence interval 3.51 ̶4.93) compared to documented migrants. Adjusting for maternal region of origin attenuated the results slightly.
Conclusion: Being undocumented is strongly associated with perinatal mortality in the offspring. Disparities were not explained by maternal origin or maternal health factors, indicating that social determinants of health through delays in receiving adequate care and factors negatively influencing gestational length may be of importance.
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