Effect of access to antenatal care on risk of preterm birth among migrant women in Italy: A population-based cohort study.

Objective: To evaluate the association between maternal migration status and preterm birth, and whether a better adherence to antenatal care during pregnancy mitigates the risk of preterm birth. Design: Population-based cohort. Setting: Administrative databases of the Lombardy region, Italy. Population: First singleton births of women aged 15-55 years at 22-42 gestational weeks, between 2016 and 2021. Methods: Assessed the risk of preterm birth (<37 weeks). Main outcome measures: A multivariable logistic regression mediation model calculated the mediation effect of adherence to antenatal care in the association between maternal migrant status and preterm birth and the residual effect not mediated by it. Analyses were adjusted for the socio-demographic and pregnant characteristics of the women. Results: Of 349,753 births in the cohort, Italian nationality accounted for 71 %; 28.4 % were documented migrants and 0.4 % undocumented migrants. Among them, 5.3 %, 6.4 %, and 9.3 % had a preterm birth, respectively. Using deliveries of Italian citizens as referent, migrants had a significantly increased risk of preterm birth (adjusted relative risk: 1.22, 95 % confidence interval: 1.18-1.27). Adherence to antenatal care mediated the 62 % of such risk. We have calculated that adherence to antenatal pathways set to the highest level for the whole population could lead to a 37 % reduction in preterm birth risk. Conclusion: Part of the excess of preterm birth among documented and undocumented migrants in Italy can be explained by a lack of adherence to the antenatal care path despite equal access to National Health care. The adherence of all pregnant women to antenatal care would reduce the risk of preterm birth by about one-third.