Area-level poverty and preterm birth risk: a population-based multilevel analysis

Towards reducing variations in infant mortality and morbidity: a population-based approach

Background

Our aims were (1) to improve understanding of regional variation in early-life mortality rates and the UK’s poor performance in international comparisons; and (2) to identify the extent to which late and moderately preterm (LMPT) birth contributes to early childhood mortality and morbidity.

Objective

To undertake a programme of linked population-based research studies to work towards reducing variations in infant mortality and morbidity rates.

Design

Two interlinked streams: (1) a detailed analysis of national and regional data sets and (2) establishment of cohorts of LMPT babies and term-born control babies.

Setting

Cohorts were drawn from the geographically defined areas of Leicestershire and Nottinghamshire, and analyses were carried out at the University of Leicester.

Data sources

For stream 1, national data were obtained from four sources: the Office for National Statistics, NHS Numbers for Babies, Centre for Maternal and Child Enquiries and East Midlands and South Yorkshire Congenital Anomalies Register. For stream 2, prospective data were collected for 1130 LMPT babies and 1255 term-born control babies.

Main outcome measures

Detailed analysis of stillbirth and early childhood mortality rates with a particular focus on factors leading to biased or unfair comparison; review of clinical, health economic and developmental outcomes over the first 2 years of life for LMPT and term-born babies.

Results

The deprivation gap in neonatal mortality has widened over time, despite government efforts to reduce it. Stillbirth rates are twice as high in the most deprived as in the least deprived decile. Approximately 70% of all infant deaths are the result of either preterm birth or a major congenital abnormality, and these are heavily influenced by mothers’ exposure to deprivation. Births at < 24 weeks’ gestation constitute only 1% of all births, but account for 20% of infant mortality. Classification of birth status for these babies varies widely across England. Risk of LMPT birth is greatest in the most deprived groups within society. Compared with term-born peers, LMPT babies are at an increased risk of neonatal morbidity, neonatal unit admission and poorer long-term health and developmental outcomes. Cognitive and socioemotional development problems confer the greatest long-term burden, with the risk being amplified by socioeconomic factors. During the first 24 months of life each child born LMPT generates approximately £3500 of additional health and societal costs.

Conclusions

Health professionals should be cautious in reviewing unadjusted early-life mortality rates, particularly when these relate to individual trusts. When more sophisticated analysis is not possible, babies of < 24 weeks’ gestation should be excluded. Neonatal services should review the care they offer to babies born LMPT to ensure that it is appropriate to their needs. The risk of adverse outcome is low in LMPT children. However, the risk appears higher for some types of antenatal problems and when the mother is from a deprived background.

Future work

Future work could include studies to improve our understanding of how deprivation increases the risk of mortality and morbidity in early life and investigation of longer-term outcomes and interventions in at-risk LMPT infants to improve future attainment.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

What contributes to disparities in the preterm birth rate in European countries?

PURPOSE OF REVIEW

In countries with comparable levels of development and healthcare systems, preterm birth rates vary markedly--a range from 5 to 10% among live births in Europe. This review seeks to identify the most likely sources of heterogeneity in preterm birth rates, which could explain differences between European countries.

RECENT FINDINGS

Multiple risk factors impact on preterm birth. Recent studies reported on measurement issues, population characteristics, reproductive health policies as well as medical practices, including those related to subfertility treatments and indicated deliveries, which affect preterm birth rates and trends in high-income countries. We showed wide variation in population characteristics, including multiple pregnancies, maternal age, BMI, smoking, and percentage of migrants in European countries.

SUMMARY

Many potentially modifiable population factors (BMI, smoking, and environmental exposures) as well as health system factors (practices related to indicated preterm deliveries) play a role in determining preterm birth risk. More knowledge about how these factors contribute to low and stable preterm birth rates in some countries is needed for shaping future policy. It is also important to clarify the potential contribution of artifactual differences owing to measurement.

A Multilevel Analysis of Neighborhood Socioeconomic Effect on Preterm Births in Georgia, USA

This study estimates the neighborhood socioeconomic status (SES) effect on the risk of preterm birth (PTB) using multilevel regression (MLR) models. Birth data retrieved from year 2000 and 2010 Georgia Vital Records were linked to their respective census tracts. Principle component analysis (PCA) was performed on nine selected census variables and the first two principal components (Fac1 and Fac2) were used to represent the neighborhood-level SES in the MLR models. Two-level random intercept MLR models were specified using 122,744 and 112,578 live and singleton births at the individual level and 1613 and 1952 census tracts at the neighborhood level, for 2000 and 2010, respectively. After adjustment for individual level factors, Fac1, which represents disadvantaged SES, respectively generated an Odds Ratio of 1.056 (95% CI: 1.031–1.081) and 1.080 (95% CI: 1.056–1.105) for these two years, showing a modest but statistically significant effect on PTB. After adjusting for individual level factors and the census tract level factors, Intra-class correlation (ICC) was 1.2% and 1.4%, for year 2000 and 2010, respectively. The two IOR-80% intervals, 0.73–1.52 (year 2000) and 0.73–1.59 (year 2010) suggest large unexplained between census tract variation. The Median Odds Ratio (MOR) value of 1.21(year 2000) and 1.23 (year 2010) revealed that the un-modeled neighborhood effect was smaller than two individual-level predictor variables, race, and tobacco use but larger than the fixed effect of census tract-level predicting variable, Fac1 and all the other individual level factors. Overall, better census tract level SES was found to have a modest protective effect for PTB risk and the effects of the two examined years were similar. Large unexplained between census tract heterogeneity warrants more sophisticated MLR models to further investigate the PTB risk factors and their interactions at both individual and neighborhood levels.

Differences in perinatal morbidity and mortality on the neighbourhood level in Dutch municipalities: a population based cohort study

BACKGROUND

In a national perinatal health programme, we observed striking heterogeneity in the explanation of the most prominent risks across municipalities. Therefore we explored the separate contribution of several socio-demographic risks on perinatal health inequalities between municipalities and neighbourhoods. The study aims to identify perinatal health inequalities on the neighbourhood level across the selected municipalities, and to objectify the contribution of socio-demographic risk factors on pregnancy outcomes in each municipality by the application of the population attributable risk concept.

METHODS

Population based cohort study (2000-2008). Perinatal outcomes of 352,407 single pregnancies from 15 municipalities were analysed. Odds ratios and population attributable risks were calculated. Main outcomes were combined perinatal morbidity (small-for-gestational age, preterm birth, congenital anomalies, and low Apgar score), and perinatal mortality.

RESULTS

Perinatal health inequalities existed on both the municipal and the neighbourhood level. In municipalities, combined perinatal morbidity ranged from 17.3 to 23.6%, and perinatal mortality ranges from 10.1 to 15.4‰. Considerable differences in low socio-economic status between municipalities were apparent, with prevalences ranging from 14.4 to 82.5%. In seven municipalities, significant differences between neighbourhoods existed for perinatal morbidity (adjusted OR ranging from 1.33 to 2.38) and for perinatal mortality (adjusted OR ranging from 2.06 to 5.59). For some municipalities, socio-demographic risk factors were s a strong predictor for the observed inequalities, but in other municipalities these factors were very weak predictors. If all socio-demographic determinants were set to the most favourable value in a predictive model, combined perinatal morbidity would decrease with 15 to 39% in these municipalities.

CONCLUSIONS

Substantial differences in perinatal morbidity and mortality between municipalities and neighbourhoods exist. Different patterns of inequality suggest differences in etiology. Policy makers and healthcare professionals need to be informed about their local perinatal health profiles in order to introduce antenatal healthcare tailored to the individual and neighbourhood environment.

Using Geographic Information Science to Explore Associations between Air Pollution, Environmental Amenities, and Preterm Births

The study uses geographic information science (GIS) and statistics to find out if there are statistical differences between full term and preterm births to non-Hispanic white, non-Hispanic Black, and Hispanic mothers in their exposure to air pollution and access to environmental amenities (green space and vendors of healthy food) in the second largest city in New England, Worcester, Massachusetts. Proximity to a Toxic Release Inventory site has a statistically significant effect on preterm birth regardless of race. The air-pollution hazard score from the Risk Screening Environmental Indicators Model is also a statistically significant factor when preterm births are categorized into three groups based on the degree of prematurity. Proximity to green space and to a healthy food vendor did not have an effect on preterm births. The study also used cluster analysis and found statistically significant spatial clusters of high preterm birth volume for non-Hispanic white, non-Hispanic Black, and Hispanic mothers.

Development of a linked perinatal data resource from state administrative and community-based program data

To demonstrate a generalizable approach for developing maternal-child health data resources using state administrative records and community-based program data. We used a probabilistic and deterministic linking strategy to join vital records, hospital discharge records, and home visiting data for a population-based cohort of at-risk, first time mothers enrolled in a regional home visiting program in Southwestern Ohio and Northern Kentucky from 2007 to 2010. Because data sources shared no universal identifier, common identifying elements were selected and evaluated for discriminating power. Vital records then served as a hub to which other records were linked. Variables were recoded into clinically significant categories and a cross-set of composite analytic variables was constructed. Finally, individual-level data were linked to corresponding area-level measures by census tract using the American Communities Survey. The final data set represented 2,330 maternal-infant pairs with both home visiting and vital records data. Of these, 56 pairs (2.4 %) did not link to either maternal or infant hospital discharge records. In a 10 % validation subset (n = 233), 100 % of the reviewed matches between home visiting data and vital records were true matches. Combining multiple data sources provided more comprehensive details of perinatal health service utilization and demographic, clinical, psychosocial, and behavioral characteristics than available from a single data source. Our approach offers a template for leveraging disparate sources of data to support a platform of research that evaluates the timeliness and reach of home visiting as well as its association with key maternal-child health outcomes.

Measuring coping in pregnant minority women

Coping strategies may help explain why some minority women experience more stress and poorer birth outcomes, so a psychometrically sound instrument to assess coping is needed. We examined the psychometric properties, readability, and correlates of coping in pregnant Black (n = 186) and Hispanic (n = 220) women using the Brief COPE. Exploratory and confirmatory factor analysis tested psychometric properties. The Flesch-Kincaid Reading Level test assessed readability. Linear regression models tested correlates of coping. Findings suggested two factors for the questionnaire: active and disengaged coping, as well as adequate reliability, validity, and readability level. For disengaged coping, Cronbach's α was .78 (English) and .70 (Spanish), and for active coping .86 (English) and .92 (Spanish). A two group confirmatory factor analysis revealed both minority groups had equivalent factor loadings. The reading level was at the sixth grade. Age, education, and gravidity were all found to be significant correlates with active coping.

Dosage effect of prenatal home visiting on pregnancy outcomes in at-risk, first-time mothers

BACKGROUND AND OBJECTIVE

Home visiting programs seek to improve care management for women at high risk for preterm birth (<37 weeks). Our objective was to evaluate the effect of home visiting dosage on preterm birth and small for gestational age (SGA) infants.

METHODS

Retrospective cohort study of women in southwest Ohio with a singleton pregnancy enrolled in home visiting before 26 weeks' gestation. Vital statistics and hospital discharge data were linked with home visiting data from 2007 to 2010 to ascertain birth outcomes. Eligibility for home visiting required ≥1 of 4 risk factors: unmarried, low income, <18 years of age, or suboptimal prenatal care. Logistic regression tested the association of gestational age at enrollment and number of home visits before 26 weeks with preterm birth. Proportional hazards analysis tested the association of total number of home visits with SGA status.

RESULTS

Among 441 participants enrolled by 26 weeks, 10.9% delivered preterm; 17.9% of infants were born SGA. Mean gestational age at enrollment was 18.9 weeks; mean number of prenatal home visits was 8.2. In multivariable regression, ≥8 completed visits by 26 weeks compared with ≤3 visits was associated with an odds ratio 0.38 for preterm birth (95% confidence interval: 0.16-0.87), while having ≥12 total home visits compared with ≤3 visits was significantly associated with a hazards ratio 0.32 for SGA (95% confidence interval: 0.15-0.68).

CONCLUSIONS

Among at-risk, first time mothers enrolled prenatally in home visiting, higher dosage of intervention is associated with reduced likelihood of adverse pregnancy outcomes.

Area-level risk factors for adverse birth outcomes: trends in urban and rural settings

BACKGROUND

Significant and persistent racial and income disparities in birth outcomes exist in the US. The analyses in this manuscript examine whether adverse birth outcome time trends and associations between area-level variables and adverse birth outcomes differ by urban-rural status.

METHODS

Alabama births records were merged with ZIP code-level census measures of race, poverty, and rurality. B-splines were used to determine long-term preterm birth (PTB) and low birth weight (LBW) trends by rurality. Logistic regression models were used to examine differences in the relationships between ZIP code-level percent poverty or percent African-American with either PTB or LBW. Interactions with rurality were examined.

RESULTS

Population dense areas had higher adverse birth outcome rates compared to other regions. For LBW, the disparity between population dense and other regions increased during the 1991-2005 time period, and the magnitude of the disparity was maintained through 2010. Overall PTB and LBW rates have decreased since 2006, except within isolated rural regions. The addition of individual-level socioeconomic or race risk factors greatly attenuated these geographical disparities, but isolated rural regions maintained increased odds of adverse birth outcomes. ZIP code-level percent poverty and percent African American both had significant relationships with adverse birth outcomes. Poverty associations remained significant in the most population-dense regions when models were adjusted for individual-level risk factors.

CONCLUSIONS

Population dense urban areas have heightened rates of adverse birth outcomes. High-poverty African American areas have higher odds of adverse birth outcomes in urban versus rural regions. These results suggest there are urban-specific social or environmental factors increasing risk for adverse birth outcomes in underserved communities. On the other hand, trends in PTBs and LBWs suggest interventions that have decreased adverse birth outcomes elsewhere may not be reaching isolated rural areas.

Neighbourhood deprivation and very preterm birth in an English and French cohort

BACKGROUND

Social factors affect the risk of very preterm birth and may affect subsequent outcomes in those born preterm. We assessed the influence of neighbourhood socio-economic characteristics on the risk and outcomes of singleton very preterm birth (<32 weeks of gestation) in two European regions with different health systems.

METHODS

Live births (n=1118) from a population-based cohort of very preterm infants in 2003 in Trent (UK) and Ile-de-France (France) regions were geocoded to their neighbourhood census tracts. Odds ratios for very preterm singleton birth by neighbourhood characteristics (unemployment rate, proportion manual workers, proportion with high school education only, non home ownership) were computed using infants enumerated in the census as a control population. The impact of neighbourhood variables was further assessed by pregnancy and delivery characteristics and short term infant outcomes.

RESULTS

Risk of very preterm singleton birth was higher in more deprived neighbourhoods in both regions (OR between 2.5 and 1.5 in the most versus least deprived quartiles). No consistent associations were found between neighbourhood deprivation and maternal characteristics or health outcomes for very preterm births, although infants in more deprived neighbourhoods were less likely to be breastfed at discharge.

CONCLUSIONS

Neighbourhood deprivation had a strong consistent impact on the risk of singleton very preterm birth in two European regions, but did not appear to be associated with maternal characteristics or infant outcomes. Differences in breastfeeding at discharge suggest that socio-economic factors may affect long term outcomes.

No improvement in socioeconomic inequalities in birthweight and preterm birth over four decades: a population-based cohort study

BACKGROUND

Birthweight and gestational age are associated with socioeconomic deprivation, but the evidence in relation to temporal changes in these associations is sparse. We investigated changes in the associations between socioeconomic status (SES) and birthweight and gestational age in Newcastle upon Tyne, North of England, during 1961-2000.

METHODS

We used population-based data from hospital neonatal records on all singleton births to mothers resident in Newcastle (births with complete covariate information n = 113,182). We used linear regression to analyse the associations between neighbourhood SES and birthweight over the entire 40-year period and by decade, and logistic regression for associations with low birthweight (LBW) and preterm birth, adjusting for potential confounders.

RESULTS

There was a significant interaction between SES and decade of birth for birthweight (p = 0.028) and preterm birth (p < 0.001). Socioeconomic gradients were similar in each decade for birthweight outcomes, but for preterm birth, socioeconomic disparities were more evident in the later decades [for 1961-70, odds ratio (OR) was 1.1, 95% CI 0.9, 1.3, for the most deprived versus the least deprived quartile, while for 1991-2000, the corresponding OR was 1.5, 95% CI 1.3, 1.7]. In each decade, there was a significant decrease in birthweight adjusted for gestational age for the most deprived compared to the least deprived SES group [1961-1970: -113.4 g (95% CI-133.0, -93.8); 1991-2000: -97.5 g (95% CI-113.0, -82.0)], while there was a significant increase in birthweight in each SES group over time.

CONCLUSIONS

Socioeconomic inequalities did not narrow over the four decades for birthweight and widened for preterm birth. Mean birthweight adjusted for gestational age increased in all socioeconomic groups, suggesting an overall increase in fetal growth.

Association of vitamin D status with socio-demographic factors in Calgary, Alberta: an ecological study using Census Canada data

BACKGROUND

Low 25-hydroxyvitamin D levels are a global health problem with northern countries such as Canada at particular risk. A number of sociodemographic factors have been reported to be associated with low vitamin D levels but prior studies have been limited by the ability of the researchers to gather this data directly from clinical trial participants. The purpose of this study was to use a novel methodology of inferring sociodemographic variables to evaluate the correlates of vitamin D levels in individuals dwelling in the City of Calgary, Alberta, Canada.

METHODS

We utilized data on vitamin D test results from Calgary Laboratory Services between January 1 2010 and August 31 2011. In addition to vitamin D level, we recorded age, sex, and vitamin D testing month as individual-level variables. We inferred sociodemographic variables by associating results with census dissemination areas and using Census Canada data to determine immigration status, education, median household income and first nations status as clustered variables. Associations between vitamin D status and the individual- and dissemination area-specific variables were examined using the population-averaged regression model by a generalized estimating equations approach to account for the clustering in the data.

RESULTS

158,327 individuals were included. Age, sex, month of vitamin D testing (at an individual level), and education, immigrant status, first nations status and income (at an aggregate level) were all statistically significant predictors of vitamin D status.

CONCLUSIONS

Vitamin D status was associated with a number of sociodemographic variables. Knowledge of these variables may improve targeted education and public health initiatives.

Poverty and language development: roles of parenting and stress

Socioeconomic status affects a variety of mental and physical health outcomes, such as language development. Indeed, with poverty, disparities in the development of language processing are arguably among the most consistently found- with decreases in vocabulary, phonological awareness, and syntax at many different developmental stages. In this review, after considering basic brain systems affected by low socioeconomic status that are important for language development and related peripartum issues, we focus on two theoretical models that link poverty with the brain systems affected in language problems. The family stress model connects poverty with parental emotional distress that affects parenting, whereas the parental investment model involves a focus on basic needs that affects children's language. Understanding the mechanisms through which poverty affects the brain, parenting behaviors and language development may have implications for identification and treatment of individuals as well as social policy.

The association of neighbourhood and individual social capital with consistent self-rated health: a longitudinal study in Brazilian pregnant and postpartum women

BACKGROUND

Social conditions, social relationships and neighbourhood environment, the components of social capital, are important determinants of health. The objective of this study was to investigate the association of neighbourhood and individual social capital with consistent self-rated health in women between the first trimester of pregnancy and six months postpartum.

METHODS

A multilevel cohort study in 34 neighbourhoods was performed on 685 Brazilian women recruited at antenatal units in two cities in the State of Rio de Janeiro, Brazil. Self-rated health (SRH) was assessed in the 1st trimester of pregnancy (baseline) and six months after childbirth (follow-up). The participants were divided into two groups: 1. Good SRH--good SRH at baseline and follow-up, and, 2. Poor SRH--poor SRH at baseline and follow-up. Exploratory variables collected at baseline included neighbourhood social capital (neighbourhood-level variable), individual social capital (social support and social networks), demographic and socioeconomic characteristics, health-related behaviours and self-reported diseases. A hierarchical binomial multilevel analysis was performed to test the association between neighbourhood and individual social capital and SRH, adjusted for covariates.

RESULTS

The Good SRH group reported higher scores of social support and social networks than the Poor SRH group. Although low neighbourhood social capital was associated with poor SRH in crude analysis, the association was not significant when individual socio-demographic variables were included in the model. In the final model, women reporting poor SRH both at baseline and follow-up had lower levels of social support (positive social interaction) [OR 0.82 (95% CI: 0.73-0.90)] and a lower likelihood of friendship social networks [OR 0.61 (95% CI: 0.37-0.99)] than the Good SRH group. The characteristics that remained associated with poor SRH were low level of schooling, Black and Brown ethnicity, more children, urinary infection and water plumbing outside the house.

CONCLUSIONS

Low individual social capital during pregnancy, considered here as social support and social network, was independently associated with poor SRH in women whereas neighbourhood social capital did not affect women's SRH during pregnancy and the months thereafter. From pregnancy and up to six months postpartum, the effect of individual social capital explained better the consistency of SRH over time than neighbourhood social capital.

Spatial analysis in support of community health intervention strategies

Using vital records and census data representing 165,136 singleton births from 2003-2006, geospatial filtering and density estimates enabled the calculation of preterm birth rates at each geographical point within three urban Ohio counties. Adjusted attributable risk calculations were used to identify risk factors associated with regions of high and low rates of preterm birth. Among the three counties, affected populations varied in size as well as in demographic composition. Variation in the risk factors from one region to another suggests that a single one size fits all intervention strategy would be unlikely to efficiently or effectively impact the complex preterm birth problem. Although more useful in areas with a heterogeneous distribution of preterm birth, application of the presented approach supports the development of efficient community-level health intervention strategies by identifying communities with the highest potential impact and allowing for the prioritization of efforts on specific risk factors within those communities.

Regional cerebral development at term relates to school-age social-emotional development in very preterm children

OBJECTIVE

Preterm children are at risk for social-emotional difficulties, including autism and attention-deficit/hyperactivity disorder. We assessed the relationship of regional brain development in preterm children, evaluated via magnetic resonance imaging (MRI) at term-equivalent postmenstrual age (TEA), to later social-emotional difficulties.

METHOD

MR images obtained at TEA from 184 very preterm infants (gestation <30 weeks or birth weight <1,250 g) were analyzed for white matter abnormalities, hippocampal volume, and brain metrics. A total of 111 infants underwent diffusion tensor imaging, which provided values for fractional anisotropy and apparent diffusion coefficient. Social-emotional development was assessed with the Infant Toddler Social and Emotional Assessment (ITSEA) at age 2 and the Strengths and Difficulties Questionnaire (SDQ) at age 5 years.

RESULTS

Higher apparent diffusion coefficient in the right orbitofrontal cortex was associated with social-emotional problems at age 5 years (peer problems, p < .01). In females, smaller hippocampal volume was associated with increased hyperactivity (p < .01), peer problems (p < .05), and SDQ total score (p < .01). In males, a smaller frontal region was associated with poorer prosocial (p < .05) scores. Many of the hippocampal findings remained significant after adjusting for birthweight z score, intelligence, social risk, immaturity at birth, and parental mental health. These associations were present in children who had social-emotional problems in similar domains at age 2 and those who did not.

CONCLUSIONS

Early alterations in regional cerebral development in very preterm infants relate to specific deficits in social-emotional performance by school-age. These results vary by gender. Our results provide further evidence for a neuroanatomical basis for behavioral challenges found in very preterm children.

Prenatal care utilization in Mississippi: racial disparities and implications for unfavorable birth outcomes

The objective of the study is to identify racial disparities in prenatal care (PNC) utilization and to examine the relationship between PNC and preterm birth (PTB), low birth weight (LBW) and infant mortality in Mississippi. Retrospective cohort from 1996 to 2003 linked Mississippi birth and infant death files was used. Analysis was limited to live-born singleton infants born to non-Hispanic white and black women (n = 292,776). PNC was classified by Kotelchuck's Adequacy of Prenatal Care Utilization Index. Factors associated with PTB, LBW and infant death were identified using multiple logistic regression after controlling for maternal age, education, marital status, place of residence, tobacco use and medical risk. About one in five Mississippi women had less than adequate PNC, and racial disparities in PNC utilization were observed. Black women delayed PNC, received too few visits, and were more likely to have either "inadequate PNC" (P < 0.0001) or "no care" (P < 0.0001) compared to white women. Furthermore, among women with medical conditions, black women were twice as likely to receive inadequate PNC compared to white women. Regardless of race, "no care" and "inadequate PNC" were strong risk factors for PTB, LBW and infant death. We provide empirical evidence to support the existence of racial disparities in PNC utilization and infant birth outcomes in Mississippi. Further study is needed to explain racial differences in PNC utilization. However, this study suggests that public health interventions designed to improve PNC utilization among women might reduce unfavorable birth outcomes especially infant mortality.

Quantifying the impact of deprivation on preterm births: a retrospective cohort study

BACKGROUND

Social deprivation is associated with higher rates of preterm birth and subsequent infant mortality. Our objective was to identify risk factors for preterm birth in the UK's largest maternity unit, with a particular focus on social deprivation, and related factors.

METHODOLOGY/PRINCIPAL FINDINGS

Retrospective cohort study of 39,873 women in Liverpool, UK, from 2002-2008. Singleton pregnancies were stratified into uncomplicated low risk pregnancies and a high risk group complicated by medical problems. Multiple logistic regression, and generalized additive models were used to explore the effect of covariates including area deprivation, smoking status, BMI, parity and ethnicity on the risk of preterm birth (34⁺⁰ weeks). In the low risk group, preterm birth rates increased with deprivation, reaching 1.6% (CI₉₅ 1.4 to 1.8) in the most deprived quintile; the unadjusted odds ratio comparing an individual in the most deprived quintile, to one in the least deprived quintile was 1.5 (CI₉₅ 1.2 to 1.9). Being underweight and smoking were both independently associated with preterm birth in the low risk group, and adjusting for these factors explained the association between deprivation and preterm birth. Preterm birth was five times more likely in the high risk group (RR 4.8 CI₉₅ 4.3 to 5.4), and there was no significant relationship with deprivation.

CONCLUSIONS

Deprivation has significant impact on preterm birth rates in low risk women. The relationship between low socio-economic status and preterm births appears to be related to low maternal weight and smoking in more deprived groups.

Socioeconomic inequalities and infant mortality of 46,470 preterm infants born in Sweden between 1992 and 2006

Studies on possible sociodemographic inequities in the survival of preterm infants are scarce. Individual and neighbourhood sociodemographic factors are related to preterm birth and to infant mortality in full-term infants. The aim here was to examine whether infant mortality in Swedish preterm infants is related to individual and neighbourhood sociodemographic factors, and to study whether the hypothesised association between neighbourhood deprivation and infant mortality persists after accounting for individual sociodemographic factors. The study included 46,470 infants with a gestational length of <37 weeks, born in Sweden between 1992 and 2006. Neighbourhood deprivation was assessed by an index (education, income, unemployment, welfare assistance) in small geographical units, and categorised into low, moderate and high deprivation. Adjusted odds ratios for infant mortality were examined in relation to individual and neighbourhood sociodemographic factors. After adjusting for maternal age, infant mortality was associated with the following sociodemographic variables: maternal non-married/non-cohabiting status, low family income, low maternal education and rural status. After full adjustment, the odds ratio [95% confidence interval] was 2.98 [2.42, 3.67] for low family income compared with high family income. An increase in infant mortality was also associated with high neighbourhood deprivation; however, this increased risk no longer remained statistically significant after adjusting for individual sociodemographic factors. In conclusion, this study showed an increased infant mortality in preterm infants born to women with a less favourable sociodemographic profile.

Neighbourhood socio-economic characteristics and the risk of preterm birth for migrant and non-migrant women: a study in a French district

Neighbourhood-level deprivation is associated with preterm birth; preterm birth rates are also higher for some, but not all migrant groups. We studied the impact of neighbourhood characteristics (a deprivation score and the proportion of foreign-born residents) on singleton preterm birth in the French district of Seine-Saint-Denis for women born in France, North Africa, sub-Saharan Africa and other countries. Multilevel logistic regression models were adjusted for maternal demographic and health care characteristics. For women born in France, the preterm birth rate rose with neighbourhood deprivation quintile (3.8% in the first to 5.7% in the fifth, adjusted odds ratio: 1.40 [95% confidence interval 1.14, 1.72]) and with increasing proportions of foreign-born residents. Preterm birth rates were not higher in more deprived neighbourhoods for women born outside of France and were lower in neighbourhoods with more foreign-born residents; in multilevel models, the inverse association with deprivation remained significant for women from sub-Saharan Africa. Area-based deprivation measures should be used with caution in populations with large numbers of migrants. These results raise questions about the health benefits of clustering for migrant communities as well as the negative consequences of acculturation.

Biopsychosocial risk factors for preterm birth and postpartum emotional well-being: a case-control study on Turkish women without chronic illnesses

AIMS AND OBJECTIVES

The study aimed to determine bio-psycho-social risk factors for preterm birth in a sample of Turkish women without chronic illnesses and evaluate their anxiety and depression in early postpartum period.

BACKGROUND

Preterm birth is a devastating event with long-term health and social implications. Studies have identified several risk factors; however, the contribution of these causes differs by ethnic groups.

DESIGN

This case-control study was conducted in a tertiary hospital in Istanbul over one year. In total, 149 preterm mothers were included in the case group and 150 term mothers who delivered in the same day with a case group woman were included in the control group. Chronic illnesses and anomalies were excluded.

METHOD

Data were gathered using a form that addressed risk factors for preterm birth. Multidimensional Scale of Perceived Social Support, Beck Depression Inventory and Spielberger's State-Trait Anxiety Inventory were administered within 24-72 hours after birth.

RESULTS

Logistic regression analysis revealed that partner's lower education (≤ 8 years), history of preterm birth, antenatal hospitalisation, genitourinary infection and irregular prenatal care were significant risk factors. Perceived social support from family and friends were significantly lower in preterm group. Preterm mothers experienced significantly more anxiety and depressive symptoms in early postpartum.

CONCLUSION

Many of the socio-economical and obstetric causes of preterm births were similar to other countries with higher preterm birth rates. Preterm births were associated with lower social support along with more anxiety and depressive symptoms in early postpartum.

RELEVANCE TO CLINICAL PRACTICE

Women who have established risk factors can be targeted for more intensive antenatal care for the prevention of preterm birth. Increased maternal anxiety and depression reveal the necessity of emotional support immediately after birth.

Do racial disparities persist in infant mortality from respiratory distress syndrome?

OBJECTIVE

To examine the subset of the infants who died in 2005 from respiratory distress syndrome to determine if racial disparities persist.

DESIGN

A secondary data analysis was performed on the data set of infants who died of respiratory distress syndrome (RDS) in the 2005 period linked birth-infant death data file (N=774).

METHODS

Logistic regression was performed to evaluate the contribution of race to RDS-related mortality.

RESULTS

When analyzed independently, Black infants were 1.3 times more likely to die of RDS mortality than White infants. After the known predictors of gestation, birth weight, and gender were added to the model, Black race was no longer a significant predictor of RDS.

CONCLUSIONS

Despite Black race having been identified as a contributor to RDS mortality in the past, race was not a predictor of RDS mortality in the 2005 cohort. Previous analyses comparing pre- and post-surfactant era mortality assumed that all eligible infants received surfactant, and Black infants did not respond as well as White infants. The 2003 birth certificate revision included surfactant administration, but only 12 states reported that data in the 2005 data set. Only 22% of eligible infants had documentation of surfactant administration. Future research is needed to confirm that eligible infants are receiving surfactant and to evaluate the response of infants by race. If Black infants do not respond to the available surfactant replacement products, genomics research is needed to explore targeted therapies for this group.

Nature of socioeconomic inequalities in neonatal mortality: population based study

OBJECTIVE

To investigate time trends in socioeconomic inequalities in cause specific neonatal mortality in order to assess changing patterns in mortality due to different causes, particularly prematurity, and identify key areas of focus for future intervention strategies.

DESIGN

Retrospective cohort study.

SETTING

England.

PARTICIPANTS

All neonatal deaths in singleton infants born between 1 January 1997 and 31 December 2007.

MAIN OUTCOME MEASURE

Cause specific neonatal mortality per 10 000 births by deprivation tenth (deprivation measured with UK index of multiple deprivation 2004 at super output area level).

RESULTS

18 524 neonatal deaths occurred in singleton infants born in the 11 year study period. Neonatal mortality fell between 1997-9 and 2006-7 (from 31.4 to 25.1 per 10 000 live births). The relative deprivation gap (ratio of mortality in the most deprived tenth compared with the least deprived tenth) increased from 2.08 in 1997-9 to 2.68 in 2003-5, before a fall to 2.35 in 2006-7. The most common causes of death were immaturity and congenital anomalies. Mortality due to immaturity before 24 weeks' gestation did not decrease over time and showed the widest relative deprivation gap (2.98 in 1997-9; 4.14 in 2003-5; 3.16 in 2006-7). Mortality rates for all other causes fell over time. For congenital anomalies, immaturity, and accidents and other specific causes, the relative deprivation gap widened between 1997-9 and 2003-5, before a slight fall in 2006-7. For intrapartum events and sudden infant deaths (only 13.5% of deaths) the relative deprivation gap narrowed slightly.

CONCLUSIONS

Almost 80% of the relative deprivation gap in all cause mortality was explained by premature birth and congenital anomalies. To reduce socioeconomic inequalities in mortality, a change in focus is needed to concentrate on these two influential causes of death. Understanding the link between deprivation and preterm birth should be a major research priority to identify interventions to reduce preterm birth.

Invited commentary: maternal effects in preterm birth--effects of maternal genotype, mitochondrial DNA, imprinting, or environment?

Preterm birth is an important public health problem. A wide range of risk factors has been investigated, of which the strongest established is a woman's previous history of preterm birth. In this issue of the Journal, Boyd et al. (Am J Epidemiol. 2009;170(11):1358-1364) and Svensson et al. (Am J Epidemiol. 2009;170(11):1365-1372), using data on singleton livebirths from national birth registers linked with multigeneration databases, found evidence that maternal genetic factors impact on the risk for preterm birth, whereas paternal and probably fetal genetic factors do not. Possible caveats include missing information, the range of maternal risk factors included in the analyses, possible misclassification of these risk factors, and possible vertical transmission of microbial flora or behaviors from mother to daughter. Weinberg and Shi (Am J Epidemiol. 2009;170(11):1373-1381) build on the evidence regarding potential mechanisms underlying the heritability of preterm birth from these 2 and other studies, to evaluate the comparative ability of different study designs to distinguish among these potential mechanisms. These studies have different strengths, and a portfolio of studies of different designs and with more detailed phenotyping than previously done will be needed to probe further the etiology of preterm birth and thereby provide tools for its control.