Amanda Langridge

Population-based trends in pregnancy hypertension and pre-eclampsia: an international comparative study

Objective The objective of this study was to compare international trends in pre-eclampsia rates and in overall pregnancy hypertension rates (including gestational hypertension, pre-eclampsia and eclampsia). Design Population data (from birth and/or hospital records) on all women giving birth were available from Australia (two states), Canada (Alberta), Denmark, Norway, Scotland, Sweden and the USA (Massachusetts) for a minimum of 6 years from 1997 to 2007. All countries used the 10th revision of the International Classification of Diseases, except Massachusetts which used the 9th revision. There were no major changes to the diagnostic criteria or methods of data collection in any country during the study period. Population characteristics as well as rates of pregnancy hypertension and pre-eclampsia were compared. Results Absolute rates varied across the populations as follows: pregnancy hypertension (3.6% to 9.1%), pre-eclampsia (1.4% to 4.0%) and early-onset pre-eclampsia (0.3% to 0.7%). Pregnancy hypertension and/or pre-eclampsia rates declined over time in most populations. This was unexpected given that factors associated with pregnancy hypertension such as pre-pregnancy obesity and maternal age are generally increasing. However, there was also a downward shift in gestational age with fewer pregnancies reaching 40 weeks. Conclusion The rate of pregnancy hypertension and pre-eclampsia decreased in northern Europe and Australia from 1997 to 2007, but increased in Massachusetts. The use of a different International Classification of Diseases coding version in Massachusetts may contribute to the difference in trend. Elective delivery prior to the due date is the most likely explanation for the decrease observed in Europe and Australia. Also, the use of interventions that reduce the risk of pregnancy hypertension and/or progression to pre-eclampsia (low-dose aspirin, calcium supplementation and early delivery for mild hypertension) may have contributed to the decline.

Maternal Conditions and Perinatal Characteristics Associated with Autism Spectrum Disorder and Intellectual Disability

Background As well as being highly comorbid conditions, autism spectrum disorders (ASD) and intellectual disability (ID) share a number of clinically-relevant phenomena. This raises questions about similarities and overlap in diagnosis and aetiological pathways that may exist for both conditions. Aims To examine maternal conditions and perinatal factors for children diagnosed with an ASD, with or without ID, and children with ID of unknown cause, compared with unaffected children. Methods The study population comprised all live singleton births in Western Australia (WA) between January 1984 and December 1999 (N = 383,153). Univariate and multivariate multinomial logistic regression models were applied using a blocked modelling approach to assess the effect of maternal conditions, sociodemographic factors, labour and delivery characteristics and neonatal outcomes. Results In univariate analyses mild-moderate ID was associated with pregnancy hypertension, asthma, urinary tract infection, some types of ante-partum haemorrhage, any type of preterm birth, elective C-sections, breech presentation, poor fetal growth and need for resuscitation at birth, with all factors showing an increased risk. Severe ID was positively associated with poor fetal growth and need for resuscitation, as well as any labour or delivery complication. In the multivariate analysis no maternal conditions or perinatal factors were associated with an increased risk of ASD without ID. However, pregnancy hypertension and small head circumference were associated with a reduced risk (OR = 0.64, 95% CI: 0.43, 0.94; OR = 0.58, 95% CI: 0.34, 0.96, respectively). For ASD with ID, threatened abortion before 20 weeks gestation and poor fetal growth were associated with an increased risk. Conclusion Findings show that indicators of a poor intrauterine environment are associated with an elevated risk of ID, while for ASD, and particularly ASD without ID, the associations are much weaker. As such, these findings highlight the importance of accounting for the absence or presence of ID when examining ASD, if we are to improve our understanding of the causal pathways associated with these conditions.

Maternal Dietary Intake of Folate and Vitamins B6 and B12 During Pregnancy and the Risk of Childhood Acute Lymphoblastic Leukemia

Our aim was to address the hypothesis that maternal dietary intake of folate during pregnancy is inversely associated with risk of acute lymphoblastic leukemia (ALL) in the offspring. Dietary intake of folate, vitamins B6 and B12 in the last 6 mo of pregnancy from 333 cases and 695 frequency-matched controls were assessed using a food frequency questionnaire. Data were analyzed using unconditional logistic regression, adjusting for study matching variables, total energy, and potentially confounding variables. Higher levels of dietary folate and B12 appeared to be associated with a decreased risk of ALL. Higher levels of vitamin B6 were associated with an increased risk. The strongest associations of ALL with these variables were seen when mothers consumed alcohol in pregnancy. Our findings are consistent with a modest protective effect of higher dietary intake of folate and vitamin B12 against ALL in the offspring, more particularly among women who drank alcohol during pregnancy. These findings are consistent with previous reports of the protective effects of a maternal diet high in fruit, vegetables, and nondairy protein sources. The vitamin B6 findings are not consistent with evidence that it is a protective factor against other cancers, and may be a chance finding.

Changes in risk factors for preterm birth in Western Australia 1984-2006.

To characterise changing risk factors of preterm birth in Western Australia between 1984 and 2006.

Obstetric profiles of foreign-born women in Western Australia using data linkage, 1998-2006

Background:  Despite Western Australia (WA) having the highest proportion of overseas‐born residents of any Australian state, no previous study has examined the general patterns of obstetric health of foreign‐born women in WA.

The International Collaboration for Autism Registry Epidemiology (iCARE): Multinational Registry-Based Investigations of Autism Risk Factors and Trends

The International Collaboration for Autism Registry Epidemiology (iCARE) is the first multinational research consortium (Australia, Denmark, Finland, Israel, Norway, Sweden, USA) to promote research in autism geographical and temporal heterogeneity, phenotype, family and life course patterns, and etiology. iCARE devised solutions to challenges in multinational collaboration concerning data access security, confidentiality and management. Data are obtained by integrating existing national or state-wide, population-based, individual-level data systems and undergo rigorous harmonization and quality control processes. Analyses are performed using database federation via a computational infrastructure with a secure, web-based, interface. iCARE provides a unique, unprecedented resource in autism research that will significantly enhance the ability to detect environmental and genetic contributions to the causes and life course of autism.

ViPAR: a software platform for the Virtual Pooling and Analysis of Research Data

Abstract Background: Research studies exploring the determinants of disease require sufficient statistical power to detect meaningful effects. Sample size is often increased through centralized pooling of disparately located datasets, though ethical, privacy and data ownership issues can often hamper this process. Methods that facilitate the sharing of research data that are sympathetic with these issues and which allow flexible and detailed statistical analyses are therefore in critical need. We have created a software platform for the Virtual Pooling and Analysis of Research data (ViPAR), which employs free and open source methods to provide researchers with a web-based platform to analyse datasets housed in disparate locations. Methods: Database federation permits controlled access to remotely located datasets from a central location. The Secure Shell protocol allows data to be securely exchanged between devices over an insecure network. ViPAR combines these free technologies into a solution that facilitates ‘virtual pooling’ where data can be temporarily pooled into computer memory and made available for analysis without the need for permanent central storage. Results: Within the ViPAR infrastructure, remote sites manage their own harmonized research dataset in a database hosted at their site, while a central server hosts the data federation component and a secure analysis portal. When an analysis is initiated, requested data are retrieved from each remote site and virtually pooled at the central site. The data are then analysed by statistical software and, on completion, results of the analysis are returned to the user and the virtually pooled data are removed from memory. Conclusions: ViPAR is a secure, flexible and powerful analysis platform built on open source technology that is currently in use by large international consortia, and is made publicly available at [ http://bioinformatics.childhealthresearch.org.au/software/vipar/ ].

The impact of monetary incentives on general fertility rates in Western Australia

Background There has been widespread international concern about declining fertility rates and the long-term negative consequences particularly for industrialised countries with ageing populations. In an attempt to boost fertility rates, the Australian Government introduced a maternity payment known as the Baby Bonus. However, major concerns have been raised that such monetary incentives would attract teenagers and socially disadvantaged groups. Methods Population-level data and generalised linear models were used to examine general fertility rates between 1995 and 2006 by socioeconomic group, maternal age group, Aboriginality and location in Western Australia prior to and following the introduction of the Baby Bonus in July 2004. Results After a steady decline in general fertility rates between 1995 and 2004, rates increased significantly from 52.2 births per 1000 women, aged between 15 and 49 years, in 2004 to 58.6 births per 1000 women in 2006. While there was an overall increase in general fertility rates after adjusting for maternal socio-demographic characteristics, there were no significant differences among maternal age groups (p=0.98), between Aboriginal and non-Aboriginal women(p=0.80), maternal residential locations (p=0.98) or socioeconomic groups (p=0.68). The greatest increase in births were among women residing in the highest socioeconomic areas who had the lowest general fertility rate in 2004 (21.5 births per 1000 women) but the highest in 2006 (38.1 births per 1000 women). Conclusions Findings suggest that for countries with similar social, economic and political climates to Australia, a monetary incentive may provide a satisfactory solution to declining general fertility rates.

Social and racial inequalities in preterm births in Western Australia, 1984 to 2006.

Preterm birth is associated with a range of childhood morbidities and in industrialised societies is the primary cause of infant mortality. Social and racial inequalities in preterm birth have been reported in North America, UK, Europe and New Zealand. This study utilised population-level data to investigate social and racial inequalities in preterm birth among Aboriginal and non-Aboriginal infants in Western Australia. All live, singleton births between 1984 and 2006 (n = 567 468) were included, and multilevel multivariable logistic regression was used to investigate relative differences in preterm infants between socio-economic groups. Aboriginal and non-Aboriginal infants were analysed separately. The prevalence of preterm births increased from 7.1% in 1984-88 to 7.5% in 1999-2003, before decreasing to 7.2% in 2004-06. Inequalities in preterm births between Aboriginal and non-Aboriginal infants increased over time, with the percentage of preterm births being almost twofold higher for Aboriginal infants (14.8%), compared with non-Aboriginal infants (7.6%). A significant portion of the disparity between Aboriginal and non-Aboriginal infants is attributable to parental socio-economic and demographic characteristics, though the disparity continues to persist even after adjustment for these factors. While the overall rates of preterm birth in Western Australia have remained fairly static over the last two decades, the disparity between Aboriginal and non-Aboriginal infants has increased and is now similar to inequalities seen 20 years ago. These findings highlight a major public health issue that should be of great concern, given the short- and long-term morbidities and complications associated with preterm birth.

Neonatal complications in public and private patients: a retrospective cohort study

Objective To use propensity score methods to create similar groups of women delivering in public and private hospitals and determine any differences in mode of delivery and neonatal outcomes between the matched groups. Design Population-based, retrospective cohort study. Setting Public and private hospitals in Western Australia. Participants Included were 93 802 public and 66 479 private singleton, term deliveries during 1998–2008, from which 32 757 public patients were matched with 32 757 private patients on the propensity score of maternal characteristics. Main outcome measures Neonatal outcomes were compared in the propensity score-matched cohorts using conditional logistic regression, adjusted for antenatal risk factors and mode of delivery. Outcomes included Apgar score <7 at 5 min, neonatal resuscitation (endotracheal intubation or external cardiac massage) and admission to a neonatal special care unit. Results No significant differences in maternal characteristics were found between the propensity score-matched groups. Private patients were more likely than their matched public counterparts to undergo prelabour caesarean section (25.2% vs 18%, p<0.0001). Public patients had lower rates of neonatal unit admission (AOR 0.67, 95% CI 0.62 to 0.73) and neonatal resuscitation (AOR 0.73, 95% CI 0.56 to 0.95), but higher rates of low Apgar scores at 5 min (AOR 1.31, 95% CI 1.06 to 1.63) despite adjustment for antenatal factors. Additional adjustment for mode of delivery reduced the resuscitation risk (AOR 0.86, 95% CI  0.63 to 1.18) but did not significantly alter the other estimates. Conclusions Propensity score methods can be used to generate comparable groups of public and private patients. Despite the rates of low Apgar scores being higher in public patients, the rates of special care admission were lower. Whether these findings stem from differences in paediatric services or clinical factors is yet to be determined.