Trends and associations between maternal characteristics and infant birthweight among Indigenous and non-Indigenous people in Tasmania, Australia: a population-based study

Abstract

ObjectiveThis study aimed to investigate the trends and associations of maternal characteristics and birthweight among Indigenous and non-Indigenous infants. Study designThis was a retrospective population-based study. MethodsFourteen years (2005–2018) of birthweight and perinatal health data of live-born singletons and their mothers obtained from the Tasmanian Data Linkage Unit were used to assess the trends and associations between maternal characteristics and infant birthweight using regression modelling. ResultsCompared with non-Indigenous mothers (n = 76,750), Indigenous mothers (n = 3805) had a significantly higher prevalence of risk factors during the 14-year period. Although the prevalence of prepregnancy obesity and gestational diabetes mellitus (GDM) markedly increased in both groups, the rate of increase was higher (P < 0.001) for Indigenous than non-Indigenous mothers. Smoking, alcohol consumption and illegal drug use during pregnancy reduced over the years, and there was no significant difference in the rate of reduction between the groups. Large-for-gestational-age (LGA) births increased while small-for-gestational-age (SGA) births decreased in both groups over time. In addition, high birthweight (HBW) births decreased while low birthweight (LBW) births increased. The rates of increase in LGA and LBW births and the rates of decrease in SGA and HBW births were significantly higher in Indigenous mothers compared with non-Indigenous mothers (P < 0.001 for all). The association between Indigenous ethnicity and LBW and SGA births weakened after adjusting for other confounding maternal and perinatal variables. LBW and SGA were positively associated with Indigenous ethnicity, age <18 years, smoking, alcohol consumption and illegal drug use, pre-eclampsia, underweight prepregnancy body mass index and low socio-economic status. Women with higher parity, pre-existing diabetes and prepregnancy overweight or obesity were more likely to give birth to an infant with HBW or LGA. ConclusionsThe prevalence of risk factors for abnormal birthweight is higher among Tasmanian Indigenous mothers, contributing to a gap in birthweight outcomes between Indigenous and non-Indigenous infants. The dramatic increase in prepregnancy obesity and GDM in both groups highlight the importance of screening and management of GDM during pregnancy. Comprehensive programmes co-designed and co-managed in consultation with Indigenous people are needed to support healthy lifestyle choices among Indigenous women to address the barriers to individuals adopting behaviour change and to help close the health outcomes–related gap between Indigenous and non-Indigenous mothers and infants.