Maternal Region of Origin and Small for Gestational Age: A Cross-sectional Analysis of Victorian Perinatal Data.

Background: Being born small for gestational age is a strong predictor of the short- and long-term health of the neonate, child, and adult. Variation in the rates of small for gestational age have been identified across population groups in high income countries, including Australia. Understanding the factors contributing to these population group differences may assist clinicians to reduce the morbidity and mortality associated with being born small. Victoria, in addition to New South Wales, accounts for the largest proportion of net overseas migration and births in Australia. The aim of this research was to analyse how migration was associated with small for gestational age in Victoria. Methods: This was a cross sectional population health study of singleton births in Victoria from 2009 to 2018 (n = 708,475). The prevalence of being born small for gestational age (SGA; < 10th centile) was determined for maternal country of origin groups. Multivariate logistic regression analysis was used to analyse the association between maternal region of origin and SGA. Results: Maternal region of origin was an independent risk factor for SGA in Victoria (p < .001), with a prevalence of SGA for migrant women of 11.3% (n = 27,815) and 7.3% for Australian born women (n = 33,749). Women from South East Asia, South Central Asia, or Sub Saharan Africa, OR 1.75 (95%CI: 1.70 to 1.8), women from North and North East Africa, Middle East, OR 1.40 (95%CI: 1.35 to 1.45) and migrant women from the Americas, Europe, and Oceania, OR1.06 (95%CI: 1.02 to 1.12) more likely to birth an SGA child in comparison to women born in Australia. Conclusions: Victorian woman’s region of origin was an independent risk factor for SGA. Variation in the rates of SGA between maternal regions of origin indicates additional factors such as, a woman’s pre migration exposures, the context of the migration journey, settlement conditions and the social environment post migration impact the potential for SGA. These findings highlight the importance of intergenerational improvements to the wellbeing of migrant women and their children. Further research is required to identify modifiable elements that contribute to birthweight differences across population groups.