Lifestyle and sociodemographic risk factors for stillbirth by region of residence in South Australia: a retrospective cohort study

Background Stillbirth rates remain a global priority and in Australia, progress has been slow. Risk factors of stillbirth are unique in Australia due to large areas of remoteness, and limited resource availability affecting the ability to identify areas of need and prevalence of factors associated with stillbirth. This retrospective cohort study describes lifestyle and sociodemographic factors associated with stillbirth in South Australia (SA), between 1998 and 2016. Methods All restigered births in SA between 1998 ad 2016 are included. The primary outcome was stillbirth (birth with no signs of life ≥ 20 weeks gestation or ≥ 400 grams if gestational age was not reported). Associations between stillbirth and lifestyle and sociodemographic factors were evaluated using multivariable logistic regression and described using adjusted odds ratios (aORs). Results A total of 363,959 births were included. Inadequate antenatal care access (assessed against the Australian Pregnancy Care Guidelines) was associated with the highest odds of stillbirth (aOR 3.93, 95% confidence interval (CI) 3.41–4.52). Other factors with important associations with stillbirth were plant/machine operation (aOR, 1.99; 95% CI, 1.16–2.45), birthing person age ≥ 40 years (aOR, 1.92; 95% CI, 1.50–2.45), paternal pensioner status (aOR, 1.83; 95% CI, 1.12–2.99), Asian country of birth (aOR, 1.58; 95% CI, 1.19–2.10) and Aboriginal/Torres Strait Islander status (aOR, 1.50; 95% CI, 1.20–1.88). The odds of stillbirth were increased in regional/remote areas in association with inadequate antenatal care (aOR, 4.64; 95% CI, 2.98–7.23), birthing age 35–40 years (aOR, 1.92; 95% CI, 1.02–3.64), Aboriginal and/or Torres Strait Islander status (aOR, 1.90; 95% CI, 1.12–3.21), paternal occupations: tradesperson (aOR, 1.69; 95% CI, 1.17–6.16) and unemployment (aOR, 4.06; 95% CI, 1.41–11.73). Conclusion Factors identified as independently associated with stillbirth odds include factors that could be addressed through timely access to adequate antenatal care and are likely relevant throughout Australia. The identified factors should be the target of stillbirth prevention strategies/efforts. The stillbirth rate in Australia is a national concern. Reducing preventable stillbirths remains a global priority.