Influence of time since naturalisation on socioeconomic status and low birth weight among immigrants in Belgium. A population-based study

BACKGROUND: Increasingly studies show that immigrants have different perinatal health outcomes compared to native-born women. Nevertheless, we lack a detailed examination of the combined effects of maternal immigrant trajectory and socioeconomic status on perinatal outcomes. Our objective was to analyze the influence of time since naturalization on low birth weight and maternal socioeconomic status in Belgium. METHODS: The data came from the linkage between the Brussels birth and death registers, the national register of migrant trajectories and the social security register for the years 2004–2010. We used logistic regression to estimate the odds ratios of the associations between low birth weight (LBW) and time since naturalization, by nationality groups, taking into account socioeconomic status (SES), parity and maternal age. RESULTS: Data relate to all singleton births to Belgian, Maghrebi, Sub-Saharan African and Turkish women (n = 76 312). The results show an U-shaped of LBW according to time since naturalization for all migrant groups. LBW declines for women naturalized since less than one year and increases significantly thereafter (p<0.0001). In parallel, we observe an increase of SES among all migrant groups. Compared to Belgians, we found a lower risk of LBW among women from Maghreb (p<0.0001) and this protection is maintained even after 10 years since naturalization. In contrast, the risk of LBW for Sub-Saharan African and Turkish mothers is lower than for Belgians after one year of naturalization but similar to that of Belgians after 10 years of naturalization. CONCLUSION: Our results show that, despite an improvement of their SES, LBW increases among Maghrebi, Sub-Saharan African and Turkish women with time since naturalization. Mothers from Maghreb have lower rates of LBW compared to Belgians and maintain their protection even after more than 10 years of having acquired the Belgian nationality. Additional studies need to be carried out in order to gain a better understanding of the association between migration trajectories, SES and perinatal health of immigrants.