Are pregnancy outcomes affected by the lack of legal status? A demographic study based on 850,288 live births in Switzerland.

Background: In the context of increased global mobility, it is fundamental to understand migrants' needs and how governments can ensure equal health opportunities for both regular and irregular migrants simply by applying low-cost primary health care measures. To identify health issues in which to intervene, this study analysed the impact of a mother's lack of legal status, together with available biological and socioeconomic characteristics, on four indicators of adverse perinatal outcomes in Switzerland.

Methods: Based on the exhaustive records of the Swiss Federal Statistical Office (FSO) for its Vital Statistics (BEVNAT), different indicators of birth outcomes, including preterm birth (PTB), low and very low birth weight (LBW and VLBW), and small for gestational age (SGA), were analysed using logistic regressions on live births occurring from 2005 to 2018. These four adverse outcomes were defined as dependent variables. Statistical analysis was performed using the statistical package STATA, version 17.

Results: Selected pregnancy outcomes were conversely affected by an irregular legal status. Analysis run on the final sample showed that, compared to the neonates of mothers who are non-migrant legal residents in Switzerland, newborns of irregular migrants have higher risks of PTB (aOR 1.18 95% CI [1.05-1.32], p<0.01) and VLBW (aOR 1.43 [1.13-1.81], p < 0.01]). In contrast, we observed that in both irregular and regular migrant groups, the odds of SGA were lowered (aOR .76 [.68-.85] p<0.01) and aOR .93 [.91-.94], p< 0.01, respectively). A similar effect was observed when controlling for any adverse outcome (any AOs) (aOR  .90 [.83-.99] p 0.022; and aOR .93 [.91-.94] p< 0.01, respectively).

Conclusions: Our results, together with those from the available literature, call for a more comprehensive assessment of all pregnancy outcomes as well as of the social determinants of health for which the analysis was adjusted. Given the complexity of the migration phenomenon, future studies should account for local structural restrictions in the organization of care, the extension of a person's network as a means of health care accessibility, diverse backgrounds and cultures and the recent arrival status of migrants. This would allow researchers to understand the long-term impact of social determinants of health on the wellbeing of a mother and child and take them into account in the adoption of health policies.