Trends in Preterm birth in the Top End of the Northern Territory, Australia: a retrospective, longitudinal cohort study characterising trends and risk factors for premature birth

Background: Preterm birth (PTB) is the single most important cause of perinatal mortality and morbidity in the developed world. In Australia, 8.6% of babies are born preterm but there is substantial variability between States and Territories. Previous reports suggest PTB rates are highest in the Northern Territory (NT), but comprehensive analysis of trends and risk factors are lacking in this region. Methods: : This was a retrospective population-based cohort study of all births documented in the in the Top End of the NT over the 10-year period from the 1st of January 2008 to 31st of December 2017. We described the overall prevalence of maternal characteristics, obstetric complications, delivery characteristics and the annual trends in PTB. The association between the characteristics and the risk of PTB risk was determined using univariate and multivariate generalised linear models producing risk ratios (RR) and adjusted RRs (aRR) respectively. Data were analysed overall, in First Nations and non-First Nations women. Results: : During the decade ending in 2017, annual rates of PTB in the Top End of the NT remained consistently close to 10% of total live births. However, First Nations women experienced more than twice the risk of PTB (16%) compared to other women (7%). Leading risk factors for PTB included premature rupture of membranes (RR 12.33), multiple pregnancy (RR 7.24), antepartum haemorrhage (RR 4.36), and pre-existing diabetes (RR 4.18). These were much more common among First Nations women. Conclusions: : First Nations women experience some of the highest PTB rates globally. Smoke exposure, socioeconomic factors, chronic diseases, and pregnancy complications are avenues for intervention, but the story is complex, and a deeper exploration is warranted. A holistic approach that also addresses key socio-demographic influences is required to improve perinatal outcomes. Trial registration: Not applicable