Increased risk of adverse maternal pregnancy outcomes among undocumented migrants in Norway

Migrants are known to have an increased risk for adverse complications during delivery. However, it is not known whether undocumented migrants have a different risk profile compared to documented migrants and non-migrants. Better knowledge about undocumented migrants' reproductive outcomes is crucial to enable targeted preventive interventions.

We performed a historical register-based population study based on numbers from the Medical Birth Registry of Norway (MBRN) from 1999 to 2020. Women aged 18-49 years with singleton births were included, in total 1,247,537 births. Legal status, i.e., undocumented migrants (without a Norwegian identity number), documented migrants (with a Norwegian identity number and born abroad) and non-migrants (with a Norwegian identity number and born in Norway), was used as the exposure. We used logistic regression to estimate the association between legal status and adverse maternal birth outcomes.

In total 5856 undocumented migrant women gave birth during the study period, representing 0.5 % of all births in Norway. Undocumented migrants had an odds ratio (OR) of 1.39 (95 % Confidence Interval (CI) 1.28-1.50) for an acute CS and OR=0.86 (95 % CI 0.76-0.98) for a planned CS, both compared to non-migrants. Similarly, the OR for severe postpartum haemorrhage (PPH) was =1.22 (95 % CI 1.03-1.43) and OR=0.69 (95 % CI=0.56-0.85) for anal sphincter injury. None of the results were significantly different when documented migrants were used as the reference group.

Undocumented migrants have an increased risk of adverse maternal birth complications compared to non-migrants, but not different from documented migrants. This indicates that for maternal birth complications, factors concerning migration may affect the risk profile to a larger degree than legal status.