Epidemiology
DOI: 10.1111/1471-0528.13047 www.bjog.org
Stillbirth rates among Indigenous and nonIndigenous women in Queensland, Australia: is the gap closing? I Ibiebele,a,b M Coory,c,d FM Boyle,b,e M Humphrey,f S Vlack,b,g V Flenadya,e a
Translating Research Into Practice (TRIP) Centre, Mater Research Institute—University of Queensland, Brisbane, Qld, Australia b School of Population Health, University of Queensland, Brisbane, Qld, Australia c Murdoch Childrens Research Institute, Melbourne, Vic., Australia d Department of Paediatrics, University of Melbourne, Melbourne, Vic., Australia e Australia and New Zealand Stillbirth Alliance, Brisbane, Qld, Australia f Queensland Maternal and Perinatal Quality Council, Brisbane, Qld, Australia g Queensland Health Metro North Brisbane Public Health Unit, Brisbane, Qld, Australia Correspondence: I Ibiebele, Translating Research Into Practice (TRIP) Centre, Mater Research Institute—University of Queensland (MRI-UQ), Level 2 Aubigny Place, Raymond Terrace, South Brisbane, Qld 4101, Australia. Email [email protected] Accepted 4 July 2014. Published Online 3 September 2014.
Objective To determine whether the disparity gap is closing
between stillbirth rates for Indigenous and non-Indigenous women and to identify focal areas for future prevention efforts according to gestational age and geographic location. Design Population-based retrospective cohort study. Setting Queensland, Australia. Population All singleton births of at least 20 weeks of gestation or
at least 400 g birthweight. Methods Routinely collected data on births were obtained for the
period 1995 to 2011. Indigenous and non-Indigenous stillbirth rates and percent reduction in the gap were compared over time and by geographic location and gestational age. Main outcome measures All-cause and cause-specific stillbirth
rates (per 1000 ongoing pregnancies). Results Over the study period there was a 57.3% reduction in the
for women in regional (57.0%) and remote (56.1%) locations, these women remained at increased risk compared with those in urban regions. There was no reduction for term stillbirths. Major conditions contributing to the disparity were maternal conditions (diabetes) (relative risk [RR] 3.78, 95% confidence intervals [95% CI] 2.59–5.51), perinatal infection (RR 3.70, 95% CI 2.54–5.39), spontaneous preterm birth (RR 3.08, 95% CI 2.51–3.77), hypertension (RR 2.22, 95% CI 1.45–3.39), fetal growth restriction (RR 1.78, 95% CI 1.17–2.71) and antepartum haemorrhage (RR 1.58, 95% CI 1.13–2.22). Conclusions The gap in stillbirth rates between Indigenous and
non-Indigenous women is closing, but Indigenous women continue to be at increased risk due to a number of potentially preventable conditions. There is little change in the gap at term gestational ages. Keywords Aboriginal and Torres Strait Islander, cause of death, fetal death, indigenous, stillbirth, trends, urban.
disparity gap. Although marked reductions in the gap were shown Please cite this paper as: Ibiebele I, Coory M, Boyle FM, Humphrey M, Vlack S, Flenady V. Stillbirth rates among Indigenous and non-Indigenous women in Queensland, Australia: is the gap closing?. BJOG 2015;122:1476–1483.
Introduction Stillbirth is devastating to families and remains a challenging problem globally, with an estimated 3 million deaths occurring during the third trimester of pregnancy each year.1 Applying the standard lower gestational age definition used in many high-income countries, the numbers of stillbirths are likely to be at least double this estimate.2 Despite significant reductions in stillbirth rates in high-income countries over the past 50 years, reduction has slowed in recent times.3 National reports from Canada4 and Australia5,6 indicate that
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stillbirth rates may be increasing. In comparison, neonatal death rates in many of these countries have continued to decline. In Australia5 and USA,7 neonatal death rates declined at a faster pace than stillbirths. Between 1990 and 2000, the fetal and neonatal death rates in USA declined by an average of 1.3% and 2.4% per year, respectively.7 Likewise, in Australia during the same period, fetal and neonatal death rates declined by an annual average rate of 1.0% and 4.5%, respectively.5,8 In Queensland during this period, fetal death rates increased by 0.14% per year while neonatal death rates decreased by 2.5% per year.9
ª 2014 Royal College of Obstetricians and Gynaecologists
Disparity gap in Indigenous stillbirth in Queensland
The need to address existing disparities across different population groups was recently highlighted as a priority in high-income countries.10 In Australia and other highincome countries, marked disparity in stillbirth rates between Indigenous and non-Indigenous populations are evident.6,11,12 A number of factors including physical and social environment, maternal behaviour, and access to and quality of health care have been suggested as contributing to this disparity.3,13 Geographic location (regional or remote residence) has been identified as an important risk factor for stillbirth in the Australian context.14,15 The study of temporal trends in rates and underlying cause of death is important to gain an understanding of the scope for further reductions in stillbirth rates and to direct further clinical and research efforts.16,17 The objective of this study was to assess the differences in stillbirth rates over time among Australian Aboriginal and Torres Strait Islander (Indigenous) and non-Indigenous women based on their geographical location and gestational age to determine whether the gap was closing. Additionally, this study aimed to assess cause-specific stillbirth rates to determine where the greatest disparities lie to identify focal areas for preventive efforts.
Methods Maternal demographic and pregnancy outcome data were obtained from the Queensland Perinatal Data Collection (QPDC) for singleton births occurring over the period 1995 to 2011. It is a requirement that all births of at least 20 weeks regardless of birthweight, and births of at least 400 g birthweight regardless of gestational age are registered in the QPDC. During 1995 to 2011, 881 654 singleton births were registered in Queensland. Of these, a total of 443 births were excluded from the analysis for the following reasons: 148 terminations of pregnancy for maternal psychosocial reasons; 270 births with unknown maternal Indigenous status; 25 births occurred at less than 20 weeks gestation and were also less than 400 g birthweight. Indigenous status was defined as whether or not the woman identified as Aboriginal and/or Torres Strait Islander. Geographic location was based on postcodes of maternal usual place of residence according to the Australian Standard Geographical Classification (ASGC) Remoteness structure,18 and was categorised as: urban (major cities), regional (inner and outer) and remote (remote and very remote). Causes of death were classified according to the Perinatal Society of Australia and New Zealand Perinatal Death Classification (PSANZ-PDC).19 The classification of cause of death available from the QPDC data set was assigned by a multidisciplinary perinatal mortality review committee as part of routine procedure. The overall autopsy rate during
ª 2014 Royal College of Obstetricians and Gynaecologists
the study period was 37.6% (25.4% among Indigenous women and 38.9% among non-Indigenous women). Autopsy rates among Indigenous women were 28.7%, 27.4% and 18.6% among urban, regional and remote residents; whereas rates among their non-Indigenous counterparts were 40.0%, 36.9% and 42.7%, respectively. Over the study period, there were four predecessors to the current PSANZ-PDC in use. These classification systems were mapped to the current PSANZ-PDC19 with minimal adjustment of subcategories to fit with the current system. A full description of the system with instructions for use is available.19 A brief description of the intent of the PSANZPDC categories is provided in the Table S1.
Outcome measures The primary outcome measures were stillbirth rate per 1000 ongoing pregnancies and cause-specific stillbirth rate per 1000 ongoing pregnancies by Indigenous status, geographic location and gestational age grouping. The gestational age groups used were
DOI: 10.1111/1471-0528.13047 www.bjog.org
Stillbirth rates among Indigenous and nonIndigenous women in Queensland, Australia: is the gap closing? I Ibiebele,a,b M Coory,c,d FM Boyle,b,e M Humphrey,f S Vlack,b,g V Flenadya,e a
Translating Research Into Practice (TRIP) Centre, Mater Research Institute—University of Queensland, Brisbane, Qld, Australia b School of Population Health, University of Queensland, Brisbane, Qld, Australia c Murdoch Childrens Research Institute, Melbourne, Vic., Australia d Department of Paediatrics, University of Melbourne, Melbourne, Vic., Australia e Australia and New Zealand Stillbirth Alliance, Brisbane, Qld, Australia f Queensland Maternal and Perinatal Quality Council, Brisbane, Qld, Australia g Queensland Health Metro North Brisbane Public Health Unit, Brisbane, Qld, Australia Correspondence: I Ibiebele, Translating Research Into Practice (TRIP) Centre, Mater Research Institute—University of Queensland (MRI-UQ), Level 2 Aubigny Place, Raymond Terrace, South Brisbane, Qld 4101, Australia. Email [email protected] Accepted 4 July 2014. Published Online 3 September 2014.
Objective To determine whether the disparity gap is closing
between stillbirth rates for Indigenous and non-Indigenous women and to identify focal areas for future prevention efforts according to gestational age and geographic location. Design Population-based retrospective cohort study. Setting Queensland, Australia. Population All singleton births of at least 20 weeks of gestation or
at least 400 g birthweight. Methods Routinely collected data on births were obtained for the
period 1995 to 2011. Indigenous and non-Indigenous stillbirth rates and percent reduction in the gap were compared over time and by geographic location and gestational age. Main outcome measures All-cause and cause-specific stillbirth
rates (per 1000 ongoing pregnancies). Results Over the study period there was a 57.3% reduction in the
for women in regional (57.0%) and remote (56.1%) locations, these women remained at increased risk compared with those in urban regions. There was no reduction for term stillbirths. Major conditions contributing to the disparity were maternal conditions (diabetes) (relative risk [RR] 3.78, 95% confidence intervals [95% CI] 2.59–5.51), perinatal infection (RR 3.70, 95% CI 2.54–5.39), spontaneous preterm birth (RR 3.08, 95% CI 2.51–3.77), hypertension (RR 2.22, 95% CI 1.45–3.39), fetal growth restriction (RR 1.78, 95% CI 1.17–2.71) and antepartum haemorrhage (RR 1.58, 95% CI 1.13–2.22). Conclusions The gap in stillbirth rates between Indigenous and
non-Indigenous women is closing, but Indigenous women continue to be at increased risk due to a number of potentially preventable conditions. There is little change in the gap at term gestational ages. Keywords Aboriginal and Torres Strait Islander, cause of death, fetal death, indigenous, stillbirth, trends, urban.
disparity gap. Although marked reductions in the gap were shown Please cite this paper as: Ibiebele I, Coory M, Boyle FM, Humphrey M, Vlack S, Flenady V. Stillbirth rates among Indigenous and non-Indigenous women in Queensland, Australia: is the gap closing?. BJOG 2015;122:1476–1483.
Introduction Stillbirth is devastating to families and remains a challenging problem globally, with an estimated 3 million deaths occurring during the third trimester of pregnancy each year.1 Applying the standard lower gestational age definition used in many high-income countries, the numbers of stillbirths are likely to be at least double this estimate.2 Despite significant reductions in stillbirth rates in high-income countries over the past 50 years, reduction has slowed in recent times.3 National reports from Canada4 and Australia5,6 indicate that
1476
stillbirth rates may be increasing. In comparison, neonatal death rates in many of these countries have continued to decline. In Australia5 and USA,7 neonatal death rates declined at a faster pace than stillbirths. Between 1990 and 2000, the fetal and neonatal death rates in USA declined by an average of 1.3% and 2.4% per year, respectively.7 Likewise, in Australia during the same period, fetal and neonatal death rates declined by an annual average rate of 1.0% and 4.5%, respectively.5,8 In Queensland during this period, fetal death rates increased by 0.14% per year while neonatal death rates decreased by 2.5% per year.9
ª 2014 Royal College of Obstetricians and Gynaecologists
Disparity gap in Indigenous stillbirth in Queensland
The need to address existing disparities across different population groups was recently highlighted as a priority in high-income countries.10 In Australia and other highincome countries, marked disparity in stillbirth rates between Indigenous and non-Indigenous populations are evident.6,11,12 A number of factors including physical and social environment, maternal behaviour, and access to and quality of health care have been suggested as contributing to this disparity.3,13 Geographic location (regional or remote residence) has been identified as an important risk factor for stillbirth in the Australian context.14,15 The study of temporal trends in rates and underlying cause of death is important to gain an understanding of the scope for further reductions in stillbirth rates and to direct further clinical and research efforts.16,17 The objective of this study was to assess the differences in stillbirth rates over time among Australian Aboriginal and Torres Strait Islander (Indigenous) and non-Indigenous women based on their geographical location and gestational age to determine whether the gap was closing. Additionally, this study aimed to assess cause-specific stillbirth rates to determine where the greatest disparities lie to identify focal areas for preventive efforts.
Methods Maternal demographic and pregnancy outcome data were obtained from the Queensland Perinatal Data Collection (QPDC) for singleton births occurring over the period 1995 to 2011. It is a requirement that all births of at least 20 weeks regardless of birthweight, and births of at least 400 g birthweight regardless of gestational age are registered in the QPDC. During 1995 to 2011, 881 654 singleton births were registered in Queensland. Of these, a total of 443 births were excluded from the analysis for the following reasons: 148 terminations of pregnancy for maternal psychosocial reasons; 270 births with unknown maternal Indigenous status; 25 births occurred at less than 20 weeks gestation and were also less than 400 g birthweight. Indigenous status was defined as whether or not the woman identified as Aboriginal and/or Torres Strait Islander. Geographic location was based on postcodes of maternal usual place of residence according to the Australian Standard Geographical Classification (ASGC) Remoteness structure,18 and was categorised as: urban (major cities), regional (inner and outer) and remote (remote and very remote). Causes of death were classified according to the Perinatal Society of Australia and New Zealand Perinatal Death Classification (PSANZ-PDC).19 The classification of cause of death available from the QPDC data set was assigned by a multidisciplinary perinatal mortality review committee as part of routine procedure. The overall autopsy rate during
ª 2014 Royal College of Obstetricians and Gynaecologists
the study period was 37.6% (25.4% among Indigenous women and 38.9% among non-Indigenous women). Autopsy rates among Indigenous women were 28.7%, 27.4% and 18.6% among urban, regional and remote residents; whereas rates among their non-Indigenous counterparts were 40.0%, 36.9% and 42.7%, respectively. Over the study period, there were four predecessors to the current PSANZ-PDC in use. These classification systems were mapped to the current PSANZ-PDC19 with minimal adjustment of subcategories to fit with the current system. A full description of the system with instructions for use is available.19 A brief description of the intent of the PSANZPDC categories is provided in the Table S1.
Outcome measures The primary outcome measures were stillbirth rate per 1000 ongoing pregnancies and cause-specific stillbirth rate per 1000 ongoing pregnancies by Indigenous status, geographic location and gestational age grouping. The gestational age groups used were
