The effectiveness of maternal pertussis vaccination for protecting Aboriginal and Torres Strait Islander infants against infection, 2012-2017: a retrospective cohort study.

OBJECTIVES: To evaluate the effectiveness of maternal pertussis vaccination for preventing pertussis infections in Aboriginal and Torres Strait Islander infants under seven months of age. STUDY DESIGN: Retrospective cohort study; analysis of linked administrative health data. SETTING, PARTICIPANTS: Mother-infant cohort (Links2HealthierBubs) including all pregnant women who gave birth to live infants (gestational age ≥ 20 weeks, birthweight ≥ 400 g) in the Northern Territory, Queensland, and Western Australia during 1 January 2012 - 31 December 2017. MAIN OUTCOME MEASURES: Proportions of women vaccinated against pertussis during pregnancy, rates of pertussis infections among infants under seven months of age, and estimated effectiveness of maternal vaccination for protecting infants against pertussis infection, each by Indigenous status. RESULTS: Of the 19 892 Aboriginal and Torres Strait Islander women who gave birth to live infants during 2012-2017, 7398 (37.2%) received pertussis vaccine doses during their pregnancy, as had 137 034 of 259 526 non-Indigenous women (52.8%; Indigenous v non-Indigenous: adjusted odds ratio, 0.66; 95% confidence interval [CI], 0.62-0.70). The annual incidence of notified pertussis infections in non-Indigenous infants declined from 16.8 (95% CI, 9.9-29) in 2012 to 1.4 (95% CI, 0.3-8.0) cases per 10 000 births in 2017; among Aboriginal and Torres Strait Islander infants, it declined from 47.6 (95% CI, 16.2-139) to 38.6 (95% CI, 10.6-140) cases per 10 000 births. The effectiveness of maternal vaccination for protecting non-Indigenous infants under seven months of age against pertussis infection during 2014-17 was 68.2% (95% CI, 51.8-79.0%); protection of Aboriginal and Torres Strait Islander infants was not statistically significant (36.1%; 95% CI, -41.3% to 71.1%). CONCLUSIONS: During 2015-17, maternal pertussis vaccination did not protect Aboriginal and Torres Strait Islander infants in the NT, Queensland, and WA against infection. Increasing the pertussis vaccination rate among pregnant Aboriginal and Torres Strait Islander women requires culturally appropriate, innovative strategies co-designed in partnership with Indigenous organisations and communities.

Mortality burden attributable to exceptional PM2.5 air pollution events in Australian cities: A health impact assessment.

Background: People living in Australian cities face increased mortality risks from exposure to extreme air pollution events due to bushfires and dust storms. However, the burden of mortality attributable to exceptional PM2.5 levels has not been well characterised. We assessed the burden of mortality due to PM2.5 pollution events in Australian capital cities between 2001 and 2020. Methods: For this health impact assessment, we obtained data on daily counts of deaths for all non-accidental causes and ages from the Australian National Vital Statistics Register. Daily concentrations of PM2.5 were estimated at a 5 km grid cell, using a Random Forest statistical model of data from air pollution monitoring sites combined with a range of satellite and land use-related data. We calculated the exceptional PM2.5 levels for each extreme pollution exposure day using the deviation from a seasonal and trend loess decomposition model. The burden of mortality was examined using a relative risk concentration-response function suggested in the literature. Findings: Over the 20-year study period, we estimated 1454 (95 % CI 987, 1920) deaths in the major Australian cities attributable to exceptional PM2.5 exposure levels. The mortality burden due to PM2.5 exposure on extreme pollution days was considerable. Variations were observed across Australia. Despite relatively low daily PM2.5 levels compared to global averages, all Australian cities have extreme pollution exposure days, with PM2.5 concentrations exceeding the World Health Organisation Air Quality Guideline standard for 24-h exposure. Our analysis results indicate that nearly one-third of deaths from extreme air pollution exposure can be prevented with a 5 % reduction in PM2.5 levels on days with exceptional pollution. Interpretation: Exposure to exceptional PM2.5 events was associated with an increased mortality burden in Australia's cities. Policies and coordinated action are needed to manage the health risks of extreme air pollution events due to bushfires and dust storms under climate change.

Associations between endometriosis and adverse pregnancy and perinatal outcomes: a population-based cohort study.

PURPOSE: To examine the association between endometriosis and adverse pregnancy and perinatal outcomes (preeclampsia, placenta previa, and preterm birth). METHODS: A population-based retrospective cohort study was conducted among 468,778 eligible women who contributed 912,747 singleton livebirths between 1980 and 2015 in Western Australia (WA). We used probabilistically linked perinatal and hospital separation data from the WA data linkage system's Midwives Notification System and Hospital Morbidity Data Collection databases. We used a doubly robust estimator by combining the inverse probability weighting with the outcome regression model to estimate adjusted risk ratios (RR) and 95% confidence intervals (CIs). RESULTS: There were 19,476 singleton livebirths among 8874 women diagnosed with endometriosis. Using a doubly robust estimator, we found pregnancies in women with endometriosis to be associated with an increased risk of preeclampsia with RR of 1.18, 95% CI 1.11-1.26, placenta previa (RR 1.59, 95% CI 1.42-1.79) and preterm birth (RR 1.45, 95% CI 1.37-1.54). The observed association persisted after stratified by the use of Medically Assisted Reproduction, with a slightly elevated risk among pregnancies conceived spontaneously. CONCLUSIONS: In this large population-based cohort, endometriosis is associated with an increased risk of preeclampsia, placenta previa, and preterm birth, independent of the use of Medically Assisted Reproduction. This may help to enhance future obstetric care among this population.

The risk of major structural birth defects associated with seasonal influenza vaccination during pregnancy: A population-based cohort study.

INTRODUCTION: Seasonal inactivated influenza vaccine (IIV) is routinely recommended during pregnancy to protect both mothers and infants from complications following influenza infection. While previous studies have evaluated the risk of major structural birth defects in infants associated with prenatal administration of monovalent pandemic IIV, fewer studies have evaluated the risk associated with prenatal seasonal IIV. METHODS: We conducted a population-based cohort study of 125,866 singleton births between 2012 and 2016 in Western Australia. Birth registrations were linked to the state's registers for congenital anomalies and a state prenatal vaccination database. We estimated prevalence ratios (PR) of any major structural birth defect and defects by organ system. Vaccinated pregnancies were defined as those with a record of IIV in the first trimester. Inverse probability treatment weighting factored for baseline probability for vaccination. A Bonferroni correction was applied to account for multiple comparisons. RESULTS: About 3.9% of births had a major structural birth defect. Seasonal IIV exposure during the first trimester was not associated with diagnosis of any major structural birth defect diagnosed within 1 month of birth (PR 0.98, 95% CI: 0.77, 1.28) or within 6 years of life (PR 1.02, 95% CI: 0.78, 1.35). We identified no increased risk in specific birth defects associated with seasonal IIV. CONCLUSION: Based on registry data for up to 6 years of follow-up, results suggest there is no association between maternal influenza vaccination and risk of major structural birth defects. These results support the safety of seasonal IIV administration during pregnancy.

Does family planning counselling during health service contact improve postpartum modern contraceptive uptake in Ethiopia? A nationwide cross-sectional study.

OBJECTIVE: This study examined the association between family planning counselling receipt during the 12 months preceding the survey and postpartum modern contraceptive uptake in Ethiopia. We hypothesised that receiving family planning counselling either within the community setting by a field health worker or at a health facility by a healthcare attendant during the 12 months preceding the survey improves postpartum modern contraceptive uptake. DESIGN: We used a cross-sectional study of the Ethiopian Demographic and Health Survey conducted in 2016. SETTING: Ethiopia. PARTICIPANTS: A total of 1650 women who gave birth during the 12 months and had contact with service delivery points during the 12 months preceding the survey. PRIMARY OUTCOME: A weighted modified Poisson regression model was used to estimate an adjusted relative risk (RR) of postpartum modern contraceptives. RESULTS: Approximately half (48%) of the women have missed the opportunity to receive family planning counselling at the health service contact points during the 12 months preceding the survey. The postpartum modern contraceptive uptake was 27%. Two hundred forty-two (30%) and 204 (24%) of the counselled and not counselled women used postpartum modern contraceptive methods, respectively. Compared with women who did not receive counselling for family planning, women who received counselling had higher contraceptive uptake (RR 1.32, 95% CI 1.04 to 1.67). CONCLUSION: Significant numbers of women have missed the opportunity of receiving family planning counselling during contact with health service delivery points. Modern contraceptive uptake among postpartum women was low in Ethiopia. Despite this, our findings revealed that family planning counselling was associated with improved postpartum modern contraceptive uptake.

Artificial intelligence (AI) to enhance breast cancer screening: protocol for population-based cohort study of cancer detection.

INTRODUCTION: Artificial intelligence (AI) algorithms for interpreting mammograms have the potential to improve the effectiveness of population breast cancer screening programmes if they can detect cancers, including interval cancers, without contributing substantially to overdiagnosis. Studies suggesting that AI has comparable or greater accuracy than radiologists commonly employ 'enriched' datasets in which cancer prevalence is higher than in population screening. Routine screening outcome metrics (cancer detection and recall rates) cannot be estimated from these datasets, and accuracy estimates may be subject to spectrum bias which limits generalisabilty to real-world screening. We aim to address these limitations by comparing the accuracy of AI and radiologists in a cohort of consecutive of women attending a real-world population breast cancer screening programme. METHODS AND ANALYSIS: A retrospective, consecutive cohort of digital mammography screens from 109 000 distinct women was assembled from BreastScreen WA (BSWA), Western Australia's biennial population screening programme, from November 2016 to December 2017. The cohort includes 761 screen-detected and 235 interval cancers. Descriptive characteristics and results of radiologist double-reading will be extracted from BSWA outcomes data collection. Mammograms will be reinterpreted by a commercial AI algorithm (DeepHealth). AI accuracy will be compared with that of radiologist single-reading based on the difference in the area under the receiver operating characteristic curve. Cancer detection and recall rates for combined AI-radiologist reading will be estimated by pairing the first radiologist read per screen with the AI algorithm, and compared with estimates for radiologist double-reading. ETHICS AND DISSEMINATION: This study has ethical approval from the Women and Newborn Health Service Ethics Committee (EC00350) and the Curtin University Human Research Ethics Committee (HRE2020-0316). Findings will be published in peer-reviewed journals and presented at national and international conferences. Results will also be disseminated to stakeholders in Australian breast cancer screening programmes and policy makers in population screening.

Association between interpregnancy interval and pregnancy complications by history of complications: a population-based cohort study.

OBJECTIVE: To examine if the association between interpregnancy interval (IPI) and pregnancy complications varies by the presence or absence of previous complications. DESIGN AND SETTING: Population-based longitudinally linked cohort study in Western Australia (WA). PARTICIPANTS: Mothers who had their first two (n=252 368) and three (n=96 315) consecutive singleton births in WA between 1980 and 2015. OUTCOME MEASURES: We estimated absolute risks (AR) of preeclampsia (PE) and gestational diabetes (GDM) for 3-60 months of IPI according to history of each outcome. We modelled IPI using restricted cubic splines and reported adjusted relative risk (RRs) with 95% CI at 3, 6, 12, 24, 36, 48 and 60 months, with 18 months as reference. RESULTS: Risks of PE and GDM were 9.5%, 2.6% in first pregnancies, with recurrence rates of 19.3% and 41.5% in second pregnancy for PE and GDM, respectively. The AR of GDM ranged from 30% to 43% across the IPI range for mothers with previous GDM compared with 2%-8% for mothers without previous GDM. For mothers with no previous PE, greater risks were observed for IPIs at 3 months (RR 1.24, 95% CI 1.07 to 1.43) and 60 months (RR 1.40, 95% CI 1.29 to 1.53) compared with 18 months. There was insufficient evidence for increased risk of PE at shorter IPIs of <18 months for mothers with previous PE. Shorter IPIs of <18 months were associated with lower risk than at IPIs of 18 months for mothers with no previous GDM. CONCLUSIONS: The associations between IPIs and risk of PE or GDM on subsequent pregnancies are modified by previous experience with these conditions. Mothers with previous complications had higher absolute, but lower RRs than mothers with no previous complications. However, IPI remains a potentially modifiable risk factor for mothers with previous complicated pregnancies.

'Links2HealthierBubs' cohort study: protocol for a record linkage study on the safety, uptake and effectiveness of influenza and pertussis vaccines among pregnant Australian women.

INTRODUCTION: Pregnant women and infants are at risk of severe influenza and pertussis infection. Inactivated influenza vaccine (IIV) and diphtheria-tetanus-acellular pertussis vaccine (dTpa) are recommended during pregnancy to protect both mothers and infants. In Australia, uptake is not routinely monitored but coverage appears sub-optimal. Evidence on the safety of combined antenatal IIV and dTpa is fragmented or deficient, and there remain knowledge gaps of population-level vaccine effectiveness. We aim to establish a large, population-based, multi-jurisdictional cohort of mother-infant pairs to measure the uptake, safety and effectiveness of antenatal IIV and dTpa vaccines in three Australian jurisdictions. This is a first step toward assessing the impact of antenatal vaccination programmes in Australia, which can then inform government policy with respect to future strategies in national vaccination programmes. METHODS AND ANALYSIS: 'Links2HealthierBubs' is an observational, population-based, retrospective cohort study established through probabilistic record linkage of administrative health data. The cohort includes births between 2012 and 2017 (~607 605 mother-infant pairs) in jurisdictions with population-level antenatal vaccination and health outcome data (Western Australia, Queensland and the Northern Territory). Perinatal data will be the reference frame to identify the cohort. Jurisdictional vaccination registers will identify antenatal vaccination status and the gestational timing of vaccination. Information on maternal, fetal and child health outcomes will be obtained from hospitalisation and emergency department records, notifiable diseases databases, developmental anomalies databases, birth and mortality registers. ETHICS AND DISSEMINATION: Ethical approval was obtained from the Western Australian Department of Health, Curtin University, the Menzies School of Health Research, the Royal Brisbane and Women's Hospital, and the West Australian Aboriginal Health Ethics Committees. Research findings will be disseminated in peer-reviewed journals, at scientific meetings, and may be incorporated into communication materials for public health agencies and the public.

Developing evidence-based recommendations for optimal interpregnancy intervals in high-income countries: protocol for an international cohort study.

INTRODUCTION: Short interpregnancy interval (IPI) has been linked to adverse pregnancy outcomes. WHO recommends waiting at least 2 years after a live birth and 6 months after miscarriage or induced termination before conception of another pregnancy. The evidence underpinning these recommendations largely relies on data from low/middle-income countries. Furthermore, recent epidemiological investigations have suggested that these studies may overestimate the effects of IPI due to residual confounding. Future investigations of IPI effects in high-income countries drawing from large, population-based data sources are needed to inform IPI recommendations. We aim to assess the impact of IPIs on maternal and child health outcomes in high-income countries. METHODS AND ANALYSIS: This international longitudinal retrospective cohort study will include more than 18 million pregnancies, making it the largest study to investigate IPI in high-income countries. Population-based data from Australia, Finland, Norway and USA will be used. Birth records in each country will be used to identify consecutive pregnancies. Exact dates of birth and clinical best estimates of gestational length will be used to estimate IPI. Administrative birth and health data sources with >99% coverage in each country will be used to identify maternal sociodemographics, pregnancy complications, details of labour and delivery, birth and child health information. We will use matched and unmatched regression models to investigate the impact of IPI on maternal and infant outcomes, and conduct meta-analysis to pool results across countries. ETHICS AND DISSEMINATION: Ethics boards at participating sites approved this research (approval was not required in Finland). Findings will be published in peer-reviewed journals and presented at international conferences, and will inform recommendations for optimal IPI in high-income countries. Findings will provide important information for women and families planning future pregnancies and for clinicians providing prenatal care and giving guidance on family planning.