High risk of macrosomia in newborns of immigrant mothers

Background In Italy live about 8.7% immigrants, which contribute to more than 15% of all deliveries taking place in Italy. We aimed to investigate whether newborns from high migratory pressure countries (HMPC) mothers have a different macrosomia and post-term pregnancy incidence compared to Italian newborns. Methods In this retrospective observational study, we analyzed data on 404.863 babies born between 2010 and 2017. Italian mothers delivered 309.658 (76.5%), HMPC mothers 88.179 (21.8%) and developed country (DC) mothers 7.026 (1.7%) babies. We analyzed the incidence of macrosomia and post term pregnancy. We estimated incidence rate (IR), unadjusted incidence rate ratio (IRR) and 95% confidence intervals (CIs) to evaluate the association between these perinatal parameters and the mother's region of birth. Results HMPC compared to Italian newborns showed a significantly higher incidence of birthweight > 4000 g (53.3 parts per thousand vs 39.1 parts per thousand, p-value < 0.001; IRR 1.4, 95%CI = 1.36-1.45), birthweight >= 4500 g. (7.0 parts per thousand vs 3.8 parts per thousand, p-value < 0.001; IRR 1.8, 95%CI = 1.67-2.0) and gestational age at birth > 41 weeks (19.9 parts per thousand vs 12.8 parts per thousand, p-value < 0.001; IRR 1.55, 95%CI = 1.47-1.64). The macrosomia incidence between HPMC and Italian newborns was significantly increased at all gestational ages (Fig. 1), especially for mothers coming from Central Eastern Europe (121.79 parts per thousand vs 91.1 parts per thousand, p-value< 0.001; IRR 1.34, 95%CI = 1.11-1.62). Conclusion In Italy immigrant status represents a risk factor for macrosomia and post-term birth, which could be related to socio-economic status and unfavorable life conditions of immigrant mothers during pregnancy.