Income inequality, parental socioeconomic status, and birth outcomes in Japan

Mediating role of gestational weight gain in the relationship between socioeconomic status and preterm birth: a Chinese population-based study

BACKGROUND

The modifiable mechanisms underlying the association between socioeconomic status (SES) and preterm birth remain unclear. This study aimed to investigate the relationship between preterm birth and maternal SES or gestational weight gain (GWG), as well as the role of GWG in mediating SES disparities in preterm birth.

METHODS

Data was from a hospital-based sub-study of physical growth and development survey for Chinese newborns with various gestational ages. Singleton newborns aged from 24 to 42weeks' gestation and their mothers were included. Using information from maternal questionnaire, a composite SES was constructed with parental education and family annual income. GWG as mediator was calculated by deducting pre-pregnancy weight from maternal weight at delivery. Logistic regression model was adopted to investigate the association of preterm birth with SES or GWG. Causal mediation analysis was performed to measure mediating effect of GWG on the pathway from SES to preterm birth.

RESULTS

After controlling for potential confounders, risk of preterm birth was reduced by 12.4% (OR = 0.876, 95%CI:0.855-0.879) for per one-kilogram increase of GWG, and risk of preterm birth was reduced by 24% (OR = 0.760, 95%CI: 0.717-0.806) for per one-unit increase of SES score. Mediation analysis supported a significant association between higher SES and decreased risk of preterm partly through higher GWG, in which estimated proportion mediated by GWG was 13.04% (95%CI: 11.89-16.25). GWG also played a significant role as a mediator when socioeconomic status was indicated by maternal education, paternal education or family income. GWG mediated approximately 11.03% (95% CI: 8.56-18.25) of the total effect of SES on very preterm birth, which was greater than that for moderate preterm birth (6.72%, 95%CI: 2.72-31.52) and late preterm birth (9.04%, 95%CI: 5.24-24.04). A series of sensitive analysis confirmed the robustness of association of interest.

CONCLUSION

Increased GWG and higher socioeconomic status are strongly associated with a lower risk of preterm birth. GWG mediates socioeconomic disparities in preterm birth, most notably in very preterm birth. Understanding this mechanism will aid in the development of interventions and policy for maternal and child health care.

Exploring the association between non-regular employment and adverse birth outcomes: an analysis of national data in Japan

Background

As few studies have explored the association between non-regular or precarious employment in parents and adverse birth outcomes, this study aimed to investigate this association using national data in Japan.

Methods

This study utilized the census data from 2020 and birth data from the vital statistics in 2021 and 2022 in the analysis. Adverse birth outcomes, including preterm birth, term low birth weight (TLBW), and small-for-gestational-age, were examined. Data linkage was conducted between birth data and census data to link parental employment statuses and educational attainments with birth data. Rates of adverse birth outcomes were calculated for each parental employment status. Additionally, regression analysis was used to determine adjusted risk ratios (RRs) of parental employment statuses for each birth outcome.

Results

After data linkage, 334,110 birth records were included in the statistical analysis. Rates for non-regular workers were consistently higher than those for regular workers across all adverse birth outcomes for maternal employment status. Results of regression analyses indicated that the risks of preterm birth for non-regular workers were statistically significantly higher than those for regular workers, both in mothers and fathers with a RR (95% confidence intervals [CIs]) of 1.053 (1.004-1.104) and 1.142 (1.032-1.264), respectively. Furthermore, the risk of TLBW birth for non-regular workers was statistically significantly higher than that for regular workers in fathers (RR [95% CI]: 1.092 [1.043-1.143]).

Conclusions

Our findings demonstrate that non-regular workers have a higher risk of some adverse birth outcomes compared to regular workers.

Hokkaido birth cohort study in Japan on the growth trajectory of children born with low birth weight until 7 years of age

BACKGROUND

Low birth weight (LBW) is a significant global health concern with potential health risks and developmental implications for infants. Catch-up growth, an accelerated growth following an inhibition period, may partially compensate for growth deficits in LBW children.

AIMS

This study investigated the prevalence of LBW and catch-up growth in height, weight, and body mass index (BMI) among LBW children in Japan, identified factors associated with LBW, and explored the potential for catch-up growth at different ages up to seven years.

STUDY DESIGN AND SUBJECTS

The Hokkaido birth cohort study included 20,926 pregnant Japanese women recruited during their first trimester from 37 hospitals and clinics. Follow-up assessments were conducted in children up to seven years of age, tracking LBW children's growth and development using the Maternal and Child Health Handbook, and providing valuable insights into catch-up growth patterns.

OUTCOME MEASURES

LBW was defined as a neonatal birth weight of <2500 g. The primary outcomes were catch-up growth in height, weight, and BMI at different ages. Z-scores were calculated to assess growth parameters with catch-up growth, defined as a change in z-score (> 0.67) between two time points.

RESULTS AND CONCLUSIONS

A LBW was prevalent in 7.6 % of the cohort, which was lower than that reported in other Japanese studies. Among LBW children, 19.3 % achieved catch-up growth in height by age seven, and 10.6 % in weight. Catch-up growth in LBW children could partially offset these deficits. Further research will help understand the long-term outcomes and inform interventions for healthy development.

Difference in risk of preterm and small-for-gestational-age birth depending on maternal occupations in Japan

OBJECTIVES

In this study, an association between the mother's occupations with preterm and small-for-gestational-age (SGA) births was investigated using national data in Japan, and individual-level birth data from the Report of Vital Statistics: Occupational and Industrial Aspects in the 2015 fiscal year were used. Preterm and SGA birth rates were calculated for each of infant characteristics, and relative risk of each type of maternal occupations (categorized into 12 types) for the outcomes was estimated using a log binomial regression model.

RESULTS

Data of 997,600 singleton births were analyzed. Among maternal occupations, preterm birth rate was highest among carrying, cleaning, packaging, and related workers (5.65%) and lowest among security workers (4.24%). SGA birth rate was highest among manufacturing process workers (5.91%) and lowest among security workers (4.00%). We found significantly elevated risks for preterm birth among manufacturing process workers compared with unemployed mothers, and significantly elevated risks for SGA birth compared with unemployed mothers were observed among sales workers, service workers, and manufacturing process workers. In contrast, security workers had a significantly decreased risk for SGA birth compared with unemployed mothers.

Association between infant mortality and parental educational level: An analysis of data from Vital Statistics and Census in Japan

This study investigated the association between parental educational level and infant mortality using data from Vital Statistics and Census in Japan. We used the Census data in 2020 and birth and mortality data from the Vital Statistics from 2018 to 2021 in Japan. Data linkage was conducted between birth data and the Census to link the educational level with parents for birth data and between the birth data and mortality data to identify births that resulted in infant mortality. Four educational levels were compared: "junior high school," "high school," "technical school or junior college," and "university." A multivariate logistic regression model was used to investigate an association between parental educational level and infant mortality using other risk factors as covariates. After the data linkage, data on 890,682 births were analyzed. The proportion of junior high school or high school graduates was higher among fathers and mothers for births with infant mortality compared with that among those for births without infant mortality; in contrast, the proportion of university graduates was lower for births with infant mortality than those without infant mortality. Regression analysis showed that mothers with junior high school or high school graduates were significantly and positively associated with infant mortality compared with those with university graduates. As a conclusion, lower educational level in mothers was positively associated with infant mortality, and it was shown that a difference in infant mortality depending on parental educational level existed in Japan.

Association of maternal nationality with preterm birth and low birth weight rates: analysis of nationwide data in Japan from 2016 to 2020

BACKGROUND

The rate of low birth weight or preterm birth is known to vary according to the birth place of mothers. However, in Japan, studies that investigated the association between maternal nationalities and adverse birth outcomes are few. In this study, we investigated the association between maternal nationalities and adverse birth outcomes.

METHODS

We obtained live birth data from the Vital Statistics 2016-2020 of the Ministry of Health, Labour, and Welfare. We used data on maternal age, sex, parity, gestational age, birth weight, number of fetuses, household occupation, paternal nationality, and maternal nationality for each infant. We compared the rates of preterm birth and low birth weight at term among mothers whose nationalities were Japan, Korea, China, Philippines, Brazil, and other countries. Log binomial regression model was used to investigate the association between maternal nationality and the two birth outcomes using the other infants' characteristics as covariates.

RESULTS

In the analysis, data on 4,290,917 singleton births were used. Mothers from Japan, Korea, China, the Philippines, Brazil, and other nations had preterm birth rates of 4.61%, 4.16%, 3.97%, 7.43%, 7.69%, and 5.61%, respectively. The low birth weight rate among Japanese mothers was 5.36% and was the highest among the maternal nationalities. Regression analysis showed that the relative risk for preterm birth among Filipino, Brazilian, and mothers from other countries (1.520, 1.329, and 1.222, respectively) was statistically significantly higher compared with Japanese mothers. In contrast, the relative risk for Korean and Chinese mothers (0.870 and 0.899, respectively) was statistically significantly lower compared with Japanese mothers. Mothers from Korea, China, the Philippines, Brazil, and other nations had a relative risk for low birth weight that was statistically significantly lower than that of Japanese mothers (0.664, 0.447, 0.867, 0.692, and 0.887, respectively).

CONCLUSIONS

Support for mothers from the Philippines, Brazil, and other countries are necessary to prevent preterm birth. A future study is necessary to investigate the differences in characteristics among mothers of different nationalities in order to uncover the reason for the high risk for low birth weight among Japanese mothers.

Analysis of an Association between Preterm Birth and Parental Educational Level in Japan Using National Data

Preterm birth rate depending on parental educational level in recent years has not been surveyed in Japan. In this study, we showed the trend in preterm birth rate depending on parental educational level from 2000 to 2020 by linking data from the Census regarding individuals' educational level and parents in birth data of the vital statistics. Four types of parental educational level, namely junior high school, high school, technical school or junior college, and university or graduate school, were compared. Slope and relative indexes of inequality for preterm birth by educational level were computed by binomial models. Data on 3,148,711 births and 381,129,294 people were used in the analysis, and data on 782,536 singleton births were used after data linkage. The preterm birth rate (%) for junior high school graduate mothers and fathers was 5.09 and 5.20 in 2020, respectively. Contrarily, the preterm birth rate (%) for parents who graduated from a university or graduate school was 4.24 for mothers and 4.39 for fathers, and the rate tended to increase as educational level decreased, irrespective of parental gender. Results of inequality indexes showed that a statistically significant inequality by parental educational level persisted from 2000 to 2020.

Detecting geographical clusters of low birth weight and/or preterm birth in Japan

In Japan, mean birth weight has significantly decreased from 3152 g in 1979 to 3018 g in 2010 and the prevalence of preterm birth (PTB) has risen to 5.7% in the last thirty years. However, the presence and magnitude of geographical differences in low birthweight (LBW) and/or PTB in Japan is not well understood. We implemented spatial analysis to identify localized clusters and hot spots of LBW and/or PTB during 2012-2016. The Japan national birth database was used in this study. A total of 5,041,685 (male: 2,587,415, female: 2,454,270) births were used for spatial analysis using empirical Bayes estimates of the incidence rate of LBW and/or PTB and spatial scan tests to detect hot-spot areas with p values calculated from Monte Carlo iterations. The most and second likely clusters were located in two areas: (1) the small islands in south-west Japan (Amami and Okinawa, Relative risk = 1.09-1.67 with p < 0.001) and (2) the cities on the base of Mt. Fuji, stretching over three neighboring prefectures of Yamanashi, Shizuoka and Kanagawa (Relative risk = 1.10-1.55 with p < 0.001), respectively. We need to optimize the medical resource allocations based on the evidence in geographical clustering of LBW and/or PTB at specific locations in Japan.

Population attributable fraction of risk factors for low birth weight in the Japan Environment and Children's Study

BACKGROUND

Low birth weight (LBW), which is considered a birth weight of <2500  g, poses significant health problems for children. However, population attributable fraction (PAF) of risk factors for LBW have not been well studied.

OBJECTIVE

We aimed to re-evaluate associations between risk factors for LBW reported in previous studies that used the Japan Environment and Children's Study (JECS) data, and to estimate the magnitude of risk using PAF.

METHODS

Data including 91,559 mother-child dyads were obtained from JECS. Risk factors identified by previous studies that used JECS data were used to calculate odds ratios for LBW using a Bayesian logistic regression model. Based on calculated odds ratios, the PAF was calculated.

RESULTS

Parity, history of adenomyosis, hypertension disorder of pregnancy, maternal age at birth, prepregnancy body mass index, gestational weight gain (GWG), maternal smoking and lead (Pb) exposure were all significantly associated with LBW. The sum of the PAF of all factors was 79.4 %, with the largest PAF among single risk factors being GWG (16.5 %); the environmental portion of the PAF (Pb exposure, 14.6 % + maternal smoking, 12.1 %) surpassed the PAF of GWG.

CONCLUSION

Our findings suggest that the number of births classified as LBW can be reduced by approximately 27% if Pb exposure is reduced to the lowest quartile and maternal smoking is eliminated. Further investigations are needed to identify unknown risk factors for LBW.

Age-specific associations of early daycare, older siblings, severe airway infection, and preterm birth with subsequent atopic diseases

BACKGROUND

The effects of infection and developmental adaptations in infancy on the prevalence of subsequent atopy-related diseases at different ages during childhood are not fully determined. This study aims to examine the similarities and differences in the age-specific association of asthma, allergic rhinitis/conjunctivitis, and atopic dermatitis with early-life infection-related factors (i.e., daycare, older siblings, and severe airway infection) and developmental adaptations (i.e., preterm birth and rapid weight gain) in children.

METHODS

In this longitudinal cohort study (n = 47,015), children were followed from 0.5 to 11 years. The potential risks and protective factors, including daycare attendance at 0.5 years, existence of older siblings, history of hospitalization due to cold/bronchitis/bronchiolitis/pneumonia during 0.5-1.5 years, preterm birth, and rapid weight gain in the first 2.5 years, were assessed using multivariable logistic regression with adjustments for potential confounders.

RESULTS

A protective association was observed between early-life daycare attendance and asthma at 5.5-9 years, which disappeared after 10 years. A protective association was also noted throughout childhood between early daycare attendance and older siblings with allergic rhinitis/conjunctivitis. However, the association between early daycare and atopic dermatitis was found to be risky during childhood. In contrast, the early-life history of hospitalization owing to cold/bronchitis/bronchiolitis/pneumonia was identified to be a risk factor for developing both asthma and allergic rhinitis/conjunctivitis. Preterm birth was a significant risk factor for childhood asthma.

CONCLUSION

Different age-specific patterns were demonstrated in the relationship between early daycare, severe airway infection, preterm birth, and atopy-related diseases in childhood.

Social Inequalities in Non-ischemic Cardiomyopathies

Heart failure (HF) has various characteristics, such as etiology, clinical course, and clinical characteristics. Several studies reported the clinical findings of the characteristics of non-ischemic cardiomyopathy. There have been issues with genetic, biochemical, or pathophysiological problems. Some studies have been conducted on non-ischemic cardiomyopathy and social factors, for instance, racial disparities in peripartum cardiomyopathy (PPCM) or the social setting of hypertrophic cardiomyopathy. However, there have been insufficient materials to consider the relationship between social factors and clinical course in non-ischemic cardiomyopathies. There were various methodologies in therapeutic interventions, such as pharmacological, surgical, or rehabilitational, and educational issues. However, interventions that could be closely associated with social inequality have not been sufficiently elucidated. We will summarize the effects of social equality, which could have a large impact on the development and progression of HF in non-ischemic cardiomyopathies.

Effect of maternal smoking during pregnancy on gestational weight gain and birthweight: A stratified analysis by pregestational weight status

INTRODUCTION

METHODS

RESULTS

CONCLUSIONS

Association Between Length of Only-Child Period During Early Childhood and Overweight at Age 8-A Population-Based Longitudinal Study in Japan

INTRODUCTION

Prior studies have shown that children who are the only child are more likely to be overweight compared to their peers with siblings, regardless of whether they are the oldest, in the middle, or youngest. The study objective was to clarify whether there is an association between the length of the only-child period and the risk of overweight in firstborns who experienced an only-child period during early childhood before their siblings were born.

METHODS

A total of 7,576 first-born boys and 7,229 first-born girls were examined from a nationwide longitudinal survey in Japan. The length of the only-child period was determined by "birth interval"; i.e., the interval between the birth of the index child and the birth of the second child. It was categorized as short (<1.5 years), moderate (between 1.5 and 4 years), long (between 4 and 8 years), and only-child (the second baby was not born for 8 years). Overweight was defined as body mass index (BMI) z-score 1 standard deviation or more at age 8. Logistic regression was used to examine the association between length of only-child period and childhood overweight, adjusting for covariates.

RESULTS

Moderate birth interval was inversely associated with being overweight in comparison with only-child in both boys (odds ratio (OR): 0.83, 95% CI, 0.72-0.96) and girls (OR: 0.75, 95% CI, 0.63-0.88). Long birth interval also showed inverse association in boys (OR: 0.78, 95% CI, 0.62-0.97), and marginal inverse association in girls (OR: 0.80, 95% CI, 0.62-1.04).

CONCLUSION

First-born children who experienced short birth intervals did not show a different overweight risk from only-child. First-born children who experienced 1.5-8 years of the birth interval had a lower risk of childhood overweight compared with only-child.

Mediating Factors Between Parental Socioeconomic Status and Small for Gestational Age in Infants: Results from the Hokkaido Study on Environment and Children's Health

OBJECTIVES

Previous studies indicated a significant association between small for gestational age (SGA) in infants and their parents' socioeconomic status (SES). Thus, this study aimed to examine if parental factors, such as maternal smoking, and the pre-pregnancy body mass index (BMI) could mediate the associations between parental SES and SGA.

METHODS

The participants of this study were pregnant women who enrolled in an ongoing birth cohort study, the Hokkaido study, during the first trimester of their pregnancies. A total of 14,593 live singleton births were included in the statistical analysis, of which 1011 (6.9%) were SGA. Two structural equation models were employed to evaluate the associations between parental SES, parental characteristics, and SGA.

RESULTS

The effect of low SES on SGA was directly mediated by maternal pre-pregnancy BMI, smoking during the third trimester, and alcohol consumption during the first trimester in the first model, which was based the assumption of independent associations between mediating factors. In the second model, which additionally considered the mediating factors from the first model, smoking during pregnancy mediated decline in parental SES, consequently increased SGA. Moreover, an increase in pregnancy smoking status increased the prevalence of lower maternal pre-pregnancy BMI and its effect on SGA.

CONCLUSIONS FOR PRACTICE

In this study, we observed the independent mediating effect of maternal pre-pregnancy BMI, smoking, and alcohol consumption during pregnancy on low SES and, consequently, SGA, with the additional mediating pathway of SES to smoking to low BMI on SGA.

Analysis of the difference in the perinatal mortality rate between white-collar and blue-collar workers in Japan, 1995-2015

OBJECTIVES

This study investigated differences in the perinatal mortality rate between white-collar and blue-collar workers.

METHODS

Data from the “Report of Vital Statistics: Occupational and Industrial Aspects” in Japan covering the period from 1995 to 2015 were used. Five-year maternal age groups from 15-19 years to 45-49 years were analyzed according to work type, and the perinatal mortality rate for each age group and the age-standardized perinatal mortality rate according to maternal age were calculated in each analyzed year. A Bayesian age-period-cohort analysis was used to estimate age, period, and cohort effects for the perinatal mortality rate according to work type. Moreover, the perinatal mortality rate ratios between types of workers were estimated for each age group, period, and cohort.

RESULTS

The estimated perinatal mortality rate ratios of blue-collar to white-collar workers were above 1 in most of the age groups and cohorts. The age effect for the perinatal mortality rate among white-collar workers was the largest in the 15-year to 19-year age group, whereas that among blue-collar workers was the largest in the 45-year to 49-year age group. Furthermore, the estimated perinatal rate ratio between white-collar and blue-collar workers tended to increase with maternal age. The magnitude of the decrease of the cohort effects on the perinatal mortality rate was rather larger in blue-collar workers in the cohorts born between 1946-1950 and 1996-2000.

CONCLUSIONS

The magnitude of the disparity markedly increased with maternal age. Thus, middle-aged blue-collar workers need more prenatal care and preventive measures for perinatal mortality than white-collar workers.

Dual use of cigarettes and electronic nicotine delivery systems during pregnancy and the risk of small for gestational age neonates

PURPOSE

The purpose of this study was to estimate the effect of cigarette smoking and electronic nicotine delivery systems (ENDS) use during pregnancy on small for gestational age (SGA).

METHODS

We used data from the 2016-2017 Arkansas Pregnancy Risk Assessment Monitoring System, estimated the risk ratio (RR) for SGA for maternal prenatal cigarette smoking-only use, cigarette smoking, and ENDS use (i.e., dual use), with no prenatal tobacco use as referent, accounting for the complex survey design. We also explored these effects for women who stopped smoking cigarettes during pregnancy among cigarette smokers and dual users.

RESULTS

Estimated adjusted RR for SGA for cigarette-only users was 1.7 (95% confidence interval [CI]: 1.1, 2.7), and 1.8 (95% CI: 1.0, 3.4) for dual users. These RR estimates increased after correcting for tobacco use misclassification. Women who were dual users (cigarette smokers and ENDS users) and continued using ENDS but stopped smoking cigarettes had an increased risk for SGA compared with nontobacco users, 3.2 (95% CI: 1.5, 6.6).

CONCLUSIONS

Our results in a population representative sample are consistent with the hypothesis that exposure to both maternal cigarette smoking and ENDS use increased the risk of SGA. Dual users still had an elevated risk of SGA after smoking cessation.

Continuous association of total bile acid levels with the risk of small for gestational age infants

The association between maternal serum total bile acid (TBA) levels and small-for-gestational-age (SGA) infants is unclear. We investigated the association between various degrees of serum TBA levels and the risk of SGA infants in a Chinese population. The current study performed a cohort study among 11811 mothers with singleton pregnancy. Subjects were divided into seven categories according to maternal serum TBA levels. Interestingly, birth sizes were reduced, whereas the rate of SGA infants was increased across increasing categories of serum TBA. Compared to category 1, adjusted ORs (95%CI) for SGA infants were 0.99 (0.82-1.21) in category 2, 1.22 (0.97-1.53) in category 3, 1.99 (1.53-2.58) in category 4, 2.91 (2.16-3.93) in category 5, 4.29 (3.33-5.54) in category 6, and 9.01 (5.99-13.53) in category 7, respectively. Furthermore, adjusted ORs (95%CI) for SGA infants for each 1-SD increase in serum TBA levels were 1.36 (1.29-1.43) among all subjects, 2.40 (1.82-3.45) among subjects without cholestasis, and 1.13 (1.06-1.22) among subjects with cholestasis, respectively. These results suggest that gestational cholestasis increases the risk of SGA infants. Additionally, our results indicate strong, continuous associations of serum TBA levels below those diagnostic of cholestasis with a decreased birth sizes and an increased risk of SGA infants.

State- and county-level income inequality and infant mortality in the USA in 2010: a cohort study

OBJECTIVES

We examined the relationship between income inequality and the risk for infant/neonatal mortality at the state and county level and tested possible mediators of this relationship.

METHODS

We first linked state and county Gini coefficients to US Vital Statistics 2010 Cohort Linked Birth and Infant Death records (n = 3,954,325). We then fit multilevel models to test whether income inequality was associated with infant/neonatal mortality. County-level factors were tested as potential mediators.

RESULTS

Adjusted analyses indicated that income inequality at the county level-but not at the state level-was associated with increased odds of infant mortality (OR 1.14, 95% CI 1.10, 1.18) and neonatal death (OR 1.17, 95% CI 1.12, 1.23). Our mediators explained most of this variation. Bivariate analyses revealed associations between 3 county-level measures-patient-to-physician ratio, the violent crime rate, and sexually transmitted infection rate-and infant and neonatal mortality. Proportion of college-educated adults was associated with decreased odds for neonatal mortality.

CONCLUSIONS

Local variations in access to care, the rate of sexually transmitted disease, and crime are associated with infant mortality, while variations in college education in addition to these mediators explain neonatal mortality. To reduce infant and neonatal mortality, experiments are needed to examine the effectiveness of policies targeted at reducing income inequality and improving healthcare access, policing, and educational opportunities.

The association between household socio-economic status, maternal socio-demographic characteristics and adverse birth and infant growth outcomes in sub-Saharan Africa: a systematic review

Adverse birth outcomes and infant undernutrition remain the leading causes of morbidity and mortality in sub-Saharan Africa (SSA). Impaired infant growth and development, which often begins during foetal development, may persist during the first 2 years of life and has been associated with higher risks of cardiometabolic diseases. This systematic review assessed the associations between maternal demographic characteristics and household socio-economic status (SES), and preterm birth (PTB), small for gestational age, low birth weight (LBW), stunting, wasting and underweight in children under 2 years of age in SSA countries. Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, we searched for publications in three electronic databases (PubMed, Scopus and ScienceDirect). Eleven studies on children under 2 years of age, in four SSA regions, published in English between 1990 and 2018, were included. All the studies were observational in design (cross-sectional or cohort studies). Maternal education was the most commonly explored exposure. Most studies (63.3%) focused on undernutrition during the first 2 years of life: LBW, PTB and stunting. Lower maternal education, maternal unemployment and lower household wealth index were the SES factors most commonly associated with adverse birth outcomes and infant undernutrition. Maternal marital status was not associated with any infant outcomes. The definitions of the SES varied, which may explain discrepancies between studies. Nutrition intervention programs in SSA need to promote education and poverty alleviation in women at reproductive age, starting from pre-pregnancy, to optimise infant growth and development and prevent the increase in the prevalence of cardiometabolic diseases.

State-level income inequality and mortality among infants born in the United States 2007-2010: A Cohort Study

BACKGROUND

United States state-level income inequality is positively associated with infant mortality in ecological studies. We exploit spatiotemporal variations in a large dataset containing individual-level data to conduct a cohort study and to investigate whether current income inequality and increases in income inequality are associated with infant and neonatal mortality risk over the period of the 2007-2010 Great Recession in the United States.

METHODS

We used data on 16,145,716 infants and their mothers from the 2007-2010 United States Statistics Linked Infant Birth and Death Records. Multilevel logistic regression was used to determine whether 1) US state-level income inequality, as measured by Z-transformed Gini coefficients in the year of birth and 2) change in Gini coefficient between 1990 and year of birth (2007-2010), predicted infant or neonatal mortality. Our analyses adjusted for both individual and state-level covariates.

RESULTS

From 2007 to 2010 there were 98,002 infant deaths: an infant mortality rate of 6.07 infant deaths per 1000 live births. When controlling for state and individual level characteristics, there was no significant relationship between Gini Z-score and infant mortality risk. However, the observed increase in the Gini Z-score was associated with a small but significant increase likelihood of infant mortality (AOR = 1.03 to 1.06 from 2007 to 2010). Similar findings were observed when the neonatal mortality was the outcome (AOR = 1.05 to 1.13 from 2007 to 2010).

CONCLUSIONS

Infants born in states with greater changes in income inequality between 1990 and 2007 to 2010 experienced a greater likelihood of infant and neonatal mortality.

Differential relationship between state-level minimum wage and infant mortality risk among US infants born to white and black mothers

BACKGROUND

Compared to other Organisation for Economic Co-operation and Development (OECD) nations, US infant mortality rates (IMRs) are particularly high. These differences are partially driven by racial disparities, with non-Hispanic black having IMRs that are twice those of non-Hispanic white. Income inequality (the gap between rich and poor) is associated with infant mortality. One proposed way to decrease income inequality (and possibly to improve birth outcomes) is to increase the minimum wage. We aimed to elucidate the relationship between state-level minimum wage and infant mortality risk using individual-level and state-level data. We also determined whether observed associations were heterogeneous across racial groups.

METHODS

Data were from US Vital Statistics 2010 Cohort Linked Birth and Infant Death records and the 2010 US Bureau of Labor Statistics. We fit multilevel logistic models to test whether state minimum wage was associated with infant mortality. Minimum wage was standardised using the z-transformation and was dichotomised (high vs low) at the 75th percentile. Analyses were stratified by mother's race (non-Hispanic black vs non-Hispanic white).

RESULTS

High minimum wage (adjusted OR (AOR)=0.93, 95% CI 0.83 to 1.03) was associated with decreased odds of infant mortality but was not statistically significant. High minimum wage was significantly associated with reduced infant mortality among non-Hispanic black infants (AOR=0.80, 95% CI 0.68 to 0.94) but not among non-Hispanic white infants (AOR=1.04, 95% CI 0.92 to 1.17).

CONCLUSIONS

Increasing the minimum wage might be beneficial to infant health, especially among non-Hispanic black infants, and thus might decrease the racial disparity in infant mortality.

Family socioeconomic position and abnormal birth weight: evidence from a Chinese birth cohort

BACKGROUND

Birth weight is a strong determinant of infant short- and long-term health outcomes. Family socioeconomic position (SEP) is usually positively associated with birth weight. Whether this association extends to abnormal birth weight or there exists potential mediator is unclear.

METHODS

We analyzed data from 14,984 mother-infant dyads from the Born in Guangzhou Cohort Study. We used multivariable logistic regression to assess the associations of a composite family SEP score quartile with macrosomia and low birth weight (LBW), and examined the potential mediation effect of maternal pre-pregnancy body mass index (BMI) using causal mediation analysis.

RESULTS

The prevalence of macrosomia and LBW was 2.62% (n = 392) and 4.26% (n = 638). Higher family SEP was associated with a higher risk of macrosomia (OR 1.30, 95% CI 0.93-1.82; OR 1.53, 95% CI 1.11-2.11; and OR 1.59, 95% CI 1.15-2.20 for the 2nd, 3rd, and 4th SEP quartile respectively) and a lower risk of LBW (OR 0.69, 95% CI 0.55-0.86; OR 0.76, 95% CI 0.61-0.94; and OR 0.61, 95% CI 0.48-0.77 for the 2nd, 3rd, and 4th SEP quartile respectively), compared to the 1st SEP quartile. We found that pre-pregnancy BMI did not mediate the associations of SEP with macrosomia and LBW.

CONCLUSIONS

Socioeconomic disparities in fetal macrosomia and LBW exist in Southern China. Whether the results can be applied to other populations should be further investigated.

Association between socioeconomic status and small-for-gestational-age in Japan: A single center retrospective cohort study

AIM

Small-for-gestational-age (SGA) status has negative health consequences in neonates and later life. Low socioeconomic status (SES) is a reported risk factor for adverse birth outcomes, such as SGA and preterm birth (PTB). The present study investigated whether maternal SES is associated with adverse outcomes in Japanese pregnant women.

METHODS

Retrospective data were collected for 1970 Japanese women with singleton pregnancies who delivered between January 2007 and December 2011 at a single center: low SES group (n = 197); and controls (n = 1773). Low SES was defined according to the criteria of the Japanese pregnant-childbirth hospitalization support policy system.

RESULTS

The low SES group included a significantly higher proportion of young women, women with single marital status, greater parity, pre-pregnancy smoking and a lack of regular employment (P < 0.001, respectively). The crude odds ratio (OR) for the association between low maternal SES and SGA was 1.80 (95% confidence interval [CI] 1.15-2.82, P = 0.010). After adjustment for baseline maternal age, parity, body mass index, smoking and gestational weight gain, the adjusted OR for the association between low maternal SES and SGA was 1.92 (95% CI 1.17-3.17, P = 0.010). No significant association was found between maternal SES and PTB.

CONCLUSION

The present results suggest that low maternal SES is associated with SGA births in the Japanese population. Mitigation of low maternal SES could be urgent public health to prevent disadvantage birth outcome.

Poor mothers, unhealthy children: the transmission of health inequalities in the INMA study, Spain

BACKGROUND

The health of pregnant women and their fetuses are especially sensitive to socioeconomic conditions. This study analyzes the impact of maternal socioeconomic status (SES), evaluated by occupation and maternal education level, in preterm births (PTBs) and in small for gestational age (SGA) fetuses, considering the effect of the potential mediating factors on the SES and birth outcomes.

METHODS

A total of 2497 mother/newborn dyads from the INMA-Spain project were studied. We examined maternal occupation and education in relation to PTB and SGA along with covariate data, using logistic regression analysis. Adjusted models for each of the outcome variables in relation to SES indicators were estimated, considering potential mediating factors.

RESULTS

About 4.7% of babies were PTB and 9.7% SGA. Full adjusted logistic regression models showed similar odds ratio (OR) for SGA in both SES indicators. Manual working women or without university studies had higher risk of SGA than their counterpart groups (OR = 1.39% CI = 1.03-1.88 and OR = 1.39% CI = 1.00-2.00, respectively). Likewise, mothers with a manual occupation were at more risk of PTB than those with a non-manual occupation (OR = 1.74 95% CI = 1.13-2.74), but there was no association between education and PTB. Smoking, pre-pregnancy BMI and underweight gain during pregnancy were significantly associated to SGA births. The mother's age, presence of complications and overweight gain during pregnancy were related to PTB.

CONCLUSION

The mother's socioeconomic disadvantage was consistently associated with birth outcomes giving rise to intergenerational transmission of health inequalities. Reducing inequalities requires eliminating the upstream causes of poverty itself.

Complications and adverse outcomes in pregnancy and childbirth among women who conceived by assisted reproductive technologies: a nationwide birth cohort study of Japan environment and children's study

BACKGROUND

Although pregnancies conceived by assisted reproductive technology (ART) have a higher risk of maternal/perinatal complications, the overall risk of adverse outcomes necessitating advanced obstetric care has not been closely examined. The present study aimed to assess and compare the risk of maternal/perinatal complications and adverse outcomes in pregnancy and childbirth conceived by ART with those conceived naturally.

METHODS

This study was conducted as a part of the Japan environment and children's study (JECS), an ongoing nationwide birth cohort study in Japan. The risk of maternal/perinatal complications and adverse outcomes was assessed by mode of conception (natural conception, ovulation induction [OI] without ART, conventional in vitro fertilization and embryo transfer [IVF-ET], or intracytoplasmic sperm injection [ICSI]) using logistic regression and generalized estimating equations controlling for potential confounders.

RESULTS

The final dataset included women who conceived naturally (N = 90,506), by OI without ART (N = 3939), by conventional IVF-ET (N = 1476), and by ICSI (N = 1671). Compared with women who conceived naturally, those who conceived by conventional IVF-ET were at higher risk of placenta previa (adjusted OR 2.90 [95% CI 1.94, 4.34]), morbidly adherent placenta (6.85 [3.88, 12.13]), and pregnancy-induced hypertension (1.40 [1.10, 1.78]) whereas those who conceived by ICSI had a higher risk of placental abruption (2.16 [1.20, 3.88]) as well as placenta previa (2.01 [1.29, 3.13]) and morbidly adherent placenta (7.81 [4.56, 13.38]). Women who conceived by ART had a higher risk of blood transfusion (conventional IVF-ET: 3.85 [2.52, 5.88]; ICSI: 3.76 [2.49, 5.66]) and ICU admission (conventional IVF-ET: 2.58 [1.11, 6.01]; ICSI: 3.45 [1.68, 7.06]) even after controlling for potential confounders. Neonates conceived by ART had a higher risk of preterm birth (conventional IVF-ET: 1.42 [1.13, 1.78]; ICSI: 1.31 [1.05, 1.64]).

CONCLUSIONS

Women who conceived by ART had a higher risk of maternal/perinatal complications necessitating advanced obstetric care. Obstetricians should be aware of the increased risk of adverse outcomes among this population.

Pathways linking socioeconomic status to small-for-gestational-age (SGA) infants among primiparae: a birth cohort study in China

OBJECTIVES

Evidence about the relationship between socioeconomic status (SES) and small-for-gestational-age (SGA) infants was insufficient among Chinese primiparae. In addition, factors that may mediate this relationship are poorly understood. The purpose of this study was to investigate the risk of and mediators between SES and SGA.

DESIGN

Retrospective cohort study.

SETTING

Wuhan, Hubei, China.

METHOD

Participants were recruited from patients who gave birth in the maternity care hospital of Wuhan between September 2012 and October 2014. Logistic regression models were used to estimate the association between SES and SGA. Pathway analysis was performed to examine the contribution of maternal lifestyles and pregnancy-induced hypertension syndrome (PIH) to the relationship between SES and SGA. Total effect, direct effect and indirect effect of SES on SGA were measured. Effect sizes were evaluated by unstandardised estimates (B) and standardised estimates (ß).

RESULTS

Among 8737 primiparae, 927 (10.61%) pregnant women had babies with SGA. High SES was inversely associated with risk of SGA (OR 0.856; 95% CI 0.737 to 0.995) after adjustment for potential confounders. Maternal obstetric characteristics, lifestyles and PIH completely mediated SES and SGA (indirect effect: B=-0.067, 95% CI -0.108 to -0.026). The indirect effect of SES was strengthened by PIH (B=-0.029), a multivitamin supplement (B=-0.021), prepregnancy body mass index (BMI) ≥18.50 (B=-0.009) and prepregnancy BMI ≥18.50 to gestational weight gain (GWG) not below the Institute of Medicine (IOM) recommendations (B=-0.003).

CONCLUSIONS

Women from high SES predicted lower risk of PIH, more chances to take a multivitamin supplement during early pregnancy, keeping prepregnancy BMI ≥18.50 kg/cm² and gaining adequate gestational weight which was not below IOM recommendations. Furthermore, lower risk of PIH, more chances to take a multivitamin supplement, prepregnancy BMI ≥18.50 kg/cm² and GWG not below IOM recommendations were associated with a lower risk of SGA infants.

Different Risk Factors for Very Low Birth Weight, Term-Small-for-Gestational-Age, or Preterm Birth in Japan

From 1985 to 2013, the mean birth weight of infants in Japan decreased from 3120 g to 3000 g, and the low-birth-weight rate among live births increased from 6.3% to 9.6%. No prospective study has elucidated the risk factors for poor fetal growth and preterm birth in recent Japanese parents, such as increased parental age, maternal body figure, assisted reproductive technology (ART), and socioeconomic status. Participants were mother–infant pairs (n = 18,059) enrolled in a prospective birth cohort in Hokkaido, Japan from 2002 to 2013. Parental characteristics were obtained via self-reported questionnaires during pregnancy. Medical records helped identify very-low-birth-weight (VLBW; <1500 g), term-small-for-gestational-age (term-SGA), and preterm-birth (PTB; <37 weeks) infants. We calculated relative risks (RRs) for PTB, VLBW, and term-SGA birth based on parental characteristics. The prevalence of PTB, VLBW, and term-SGA was 4.5%, 0.4%, and 6.5%, respectively. Aged parents and ART were risk factors for PTB and VLBW. Maternal alcohol drinking during pregnancy increased the risk; a parental educational level of ≥16 years reduced risk of term-SGA. Maternal pre-pregnancy BMI of <18.5 kg/m² increased the risk of PTB and term-SGA. The RR for low BMI was highest among mothers who have low educational level. Among various factors, appropriate nutritional education to maintain normal BMI is important to prevent PTB and term-SGA in Japan.

Parental Socioeconomic Status and Weight Faltering in Infants in Japan

Background: Previous studies in the UK and Denmark found no significant association between low socioeconomic status (SES) and weight faltering. However, to our knowledge, there are no studies from other developed countries. We examined the association between parental SES and weight faltering in infants up to 1.5 years of age, and investigated whether the inequalities changed between 2001 and 2010 in Japan. Methods: We used data from two Japanese population-based birth cohorts started in 2001 (n = 34,594) and 2010 (n = 21,189). Parental SES was assessed as household income and parental education when the infant was 6 months old. Weight faltering was defined as the slowest weight gaining in 5% of all children in each cohort. Logistic regression analyses were conducted with adjustment for covariates. The relative index of inequality was used to assess relative impact of parental SES on weight faltering. Results: Infants in the lowest quartile of household income were 1.29 (95% confidence interval [CI]: 1.10, 1.52) and 1.27 (95% CI: 1.03, 1.56) times more likely to experience weight faltering than those in the highest income quartile both in the 2001 and 2010 cohorts, respectively. The relative index of inequality for household income was 1.66 (95% CI: 1.36, 1.96) in 2001 and 1.86 (95% CI: 1.42, 2.31) in 2010. Conclusions: Infants from lower income families have a greater risk of weight faltering in Japan. Additionally, the income-related inequalities in weight faltering did not change between the two cohorts. Social policies to address maldistribution of weight faltering due to household income are needed.

Influence of socioeconomic factors on pregnancy outcome in women with structural heart disease

Objective

Cardiac disease is the leading cause of indirect maternal mortality. The aim of this study was to analyse to what extent socioeconomic factors influence the outcome of pregnancy in women with heart disease.

Methods

The Registry of Pregnancy and Cardiac disease is a global prospective registry. For this analysis, countries that enrolled ≥10 patients were included. A combined cardiac endpoint included maternal cardiac death, arrhythmia requiring treatment, heart failure, thromboembolic event, aortic dissection, endocarditis, acute coronary syndrome, hospitalisation for cardiac reason or intervention. Associations between patient characteristics, country characteristics (income inequality expressed as Gini coefficient, health expenditure, schooling, gross domestic product, birth rate and hospital beds) and cardiac endpoints were checked in a three-level model (patient–centre–country).

Results

A total of 30 countries enrolled 2924 patients from 89 centres. At least one endpoint occurred in 645 women (22.1%). Maternal age, New York Heart Association classification and modified WHO risk classification were associated with the combined endpoint and explained 37% of variance in outcome. Gini coefficient and country-specific birth rate explained an additional 4%. There were large differences between the individual countries, but the need for multilevel modelling to account for these differences disappeared after adjustment for patient characteristics, Gini and country-specific birth rate.

Conclusion

While there are definite interregional differences in pregnancy outcome in women with cardiac disease, these differences seem to be mainly driven by individual patient characteristics. Adjustment for country characteristics refined the results to a limited extent, but maternal condition seems to be the main determinant of outcome.

Decomposition of socioeconomic inequalities in preterm deliveries in Tehran, Iran

OBJECTIVE

To investigate associations between economic inequality in preterm delivery.

METHODS

The present secondary analysis included cross-sectional data collected in interviews with patients following delivery at 103 hospitals in Tehran, Iran, between July 6 and 21, 2015. Principal component analysis was used to measure the socioeconomic status of participants and the concentration index was used to measure inequalities in preterm delivery among patients of different socioeconomic status.

RESULTS

Data were included from 5170 patients. The concentration index for preterm delivery was 0.087 (95% confidence interval 0.036-0.134), indicating that preterm deliveries were concentrated among patients with higher socioeconomic status. Higher socioeconomic status (94%), younger maternal age (29%), younger paternal age (21%), and being a homemaker (17%) had the highest positive contributions to the measured inequalities in preterm deliveries; vaginal delivery (-58%) had the highest negative contribution.

CONCLUSION

Preterm deliveries were distributed unequally among the study patients in Iran, and were concentrated among patients of higher socioeconomic status. Alongside future etiological studies, reproductive programs in Iran should focus on this population to redress the observed inequality.

Association of maternal age with child health: A Japanese longitudinal study

Average maternal age at birth has been rising steadily in Western and some Asian countries. Older maternal age has been associated with adverse pregnancy and birth outcomes; however, studies on the relationship between maternal age and young children’s health remain scarce. Therefore, we sought to investigate the association of maternal age with child health outcomes in the Japanese population. We analyzed data from two birth cohorts of the nationwide Japanese Longitudinal Survey of Babies in 21^st Century (n₂₀₀₁ = 47,715 and n₂₀₁₀ = 38,554). We estimated risks of unintentional injuries and hospital admissions at 18 and 66 months according to maternal age, controlling for the following potential confounders: parental education; maternal parity, smoking status, and employment status; household income; paternal age, and sex of the child. We also included the following as potential mediators: preterm births and birthweight. We observed a decreasing trend in the risks of children’s unintentional injuries and hospital admissions at 18 months according to maternal age in both cohorts. In the 2001 cohort, compared to mothers <25 years, odds ratios of hospital admission at 18 months were 0.97 [95% CI: 0.86, 1.09], 0.92 [0.81, 1.05], 0.76 [0.65, 0.90], and 0.71 [0.51, 0.98] for mothers aged 25.0–29.9, 30.0–34.9, 35.0–39.9, and >40.0 years, respectively, controlling for confounders. Our findings were in line with previous findings from population-based studies conducted in the United Kingdom and Canada suggesting that older maternal age may be beneficial for early child health.

Overview of Longitudinal Survey of Newborns in the 21st Century: Factors Affecting Infant Growth

There are two major nationwide birth cohort studies in Japan, namely, the Longitudinal Survey of Newborns in the 21st Century conducted by the Ministry of Health, Labor and Welfare (MHLW) and the Japan Environment and Children's Study (JECS) conducted by the Ministry of Environment. The former was a longitudinal questionnaire survey focusing on environmental and socioeconomic factors for descriptive epidemiology conducted every year since 2001 by mail. The latter was based on 15 unit centers nationwide with environmental measurements and collection of biological samples for environmental risk evaluation. Both are prospective birth cohort studies whose findings will be expected as the basis for establishing health policies. The data obtained in the former study can be used for research with permission from MHLW. To date, there have been more than ten published studies using those data. We have reviewed these studies and introduced our preliminary findings on factors affecting infant growth. Employment before delivery, educational background of parents, household income, and smoking habit of both parents have been suggested to affect infant growth. We will analyze the associations between socioeconomic factors and infant growth trajectory to elucidate the most adequate intervention for children.

Effects of a novel positive psychological intervention on prenatal stress and well-being: A pilot randomised controlled trial

PROBLEM

Low prenatal well-being has adverse outcomes for mother and infant but few interventions currently exist to promote and maintain prenatal well-being.

BACKGROUND

Mindfulness and gratitude based interventions consistently demonstrate benefits in diverse populations. Interventions integrating these constructs have potential to improve psychological and physiological health during pregnancy.

AIM

The aim of this pilot study is to examine the effect of a novel gratitude and mindfulness based intervention on prenatal stress, cortisol levels, and well-being.

METHODS

A pilot randomised controlled trial was conducted with 46 pregnant women. Participants used an online mindfulness and gratitude intervention 4 times a week for 3 weeks. Measures of prenatal stress, salivary cortisol, gratitude, mindfulness, and satisfaction with life were completed at baseline, 1.5 weeks later, and 3 weeks later.

FINDINGS

Intervention participants demonstrated significant reductions in prenatal stress in comparison to the control condition (p=.04). Within subjects reductions in waking (p=.004) and evening cortisol (p>.001) measures were observed for intervention participants. Significant effects were not observed for other well-being outcomes.

DISCUSSION

Reducing self-report and physiological stress in pregnancy can improve maternal and infant outcomes. The findings of this pilot study indicate potential direct effects of the intervention on self-reported stress in comparison to a treatment-as-usual control. Effects on a biomarker of stress, cortisol, were also observed within the intervention group.

CONCLUSION

A brief mindfulness and gratitude based intervention has the potential to reduce stress in pregnancy. Future research is needed to further explore mechanisms and potential benefits of such interventions.

[Epidemiology and risk factors of preterm birth]

OBJECTIVE

To synthesize the available evidence regarding the incidence and several risk factors of preterm birth. To describe neonatal outcomes according to gestational age and to the context of delivery.

MATERIALS AND METHODS

Consultation of the Medline database.

RESULTS

In 2010, 11% of live births (15 million babies) occurred before 37 completed weeks of gestation worldwide. About 85% of these births were moderate to late preterm babies (32-36 weeks), 10% were very preterm babies (28-31 weeks) and 5% were extremely preterm babies (<28 weeks). In France, premature birth concerns 60,000 neonates every year, 12,000 of whom are born before 32 completed weeks of gestation. Half of them are delivered after spontaneous onset of labor or preterm premature rupture of the membranes, and the other half are provider-initiated preterm births. Several maternal factors are associated with preterm birth, including sociodemographic, obstetrical, psychological, and genetic factors; paternal and environmental factors are also involved. Gestational age is highly associated with neonatal mortality and with short- and long-term morbidities. Pregnancy complications and the context of delivery also have an impact on neonatal outcomes.

CONCLUSION

Preterm birth is one of the leading cause of the under-five mortality and of neurodevelopmental impairment worldwide; it remains a major public health issue.

Preterm Birth in the Context of Increasing Income Inequality

OBJECTIVE

Preterm birth is a leading cause of infant morbidity and mortality. Little is known about the contextual effect of U.S. income inequality on preterm birth, an issue of increasing concern given that the current economic divide is the largest since 1928.

METHODS

We examined changes in inequality over time in relation to preterm birth among singleton deliveries from an electronic medical record-based cohort (n = 223,512) conducted in 11 U.S. states and the District of Columbia from 2002 to 2008. Increasing income inequality was defined as a positive change in state-level Gini coefficient from the year prior to birth. Multi-level models estimated the independent effect of increasing inequality on preterm birth (>22 and <37 weeks) controlling for maternal demographics, health behaviors, insurance status, chronic medical conditions, and state-level poverty and unemployment during the year of birth.

RESULTS

The preterm birth rate was 12.3% where inequality increased and 10.9% where it did not. After adjustment, increasing inequality remained significantly associated with preterm birth (adjusted odds ratio 1.07, 95% confidence interval 1.04, 1.11). We observed no significant interaction by insurance status or race, suggesting that increasing inequality had a broad effect across the population.

CONCLUSIONS

The contextual effect of increasing income inequality on preterm birth risk merits further study.

Socioeconomic disparities in preterm birth and birth weight in a non-Western developed setting: evidence from Hong Kong's 'Children of 1997' birth cohort

BACKGROUND

Preterm birth (PTB), low birth weight and small-for-gestational age (SGA) are associated with lower socioeconomic position (SEP) in developed Western settings, but it is unclear if such disparities persist to the same extent elsewhere, and whether associations differ by measure of SEP used. Here, we assessed the association of SEP with PTB, birth weight and SGA in the recently developed non-Western setting of Hong Kong where few women smoke or use alcohol.

METHODS

We used multivariable logistic and linear regression to assess the associations of parental and neighbourhood SEP with PTB, birth weight and SGA among 8173 singleton births from the Hong Kong population-representative 'Children of 1997' birth cohort.

RESULTS

The only measure of SEP associated with PTB was type of housing adjusted for maternal age (p for trend 0.046). Highest paternal education had a small positive association with birth weight adjusted for gestational age (21 g, 95% CI 0.2 to 43 g for ≥grade 12 compared with ≤grade 9), as did residing in private compared with public housing (21 g, 95% CI 3 to 39 g). However, these associations did not persist after adjusting for mother's age. Lower neighbourhood Gini coefficient adjusted for mother's age was associated with a lower risk of SGA (OR 0.78, 95% CI 0.63 to 0.98). None of these associations remained after adjusting for multiple comparisons.

CONCLUSIONS

PTB, birth weight and SGA may be less clearly socially patterned in Hong Kong than other developed settings, highlighting the need for setting-specific interventions to prevent adverse birth outcomes.

Association Between Maternal Smoking During Pregnancy and Birth Weight: An Appropriately Adjusted Model From the Japan Environment and Children's Study

Background

There has been no large nationwide population-based study to examine the effects of maternal smoking status during pregnancy on birth weight that simultaneously controlled for clinical information, socioeconomic status, and maternal weight. Thus, this study aimed to determine the association between maternal smoking status during pregnancy and birth weight, while taking these confounding factors into consideration.

Methods

This study examined the first-year fixed dataset from a large nationwide birth cohort study that commenced in 2011. The dataset consisted of information on 9369 singleton infants born before December 31, 2011. Children were divided into 4 groups for statistical analysis: those born to mothers who did not smoke (NS), who quit smoking before pregnancy, who quit smoking during early pregnancy, and who smoked (SM). Multiple linear regression models were conducted for each sex to examine the association between maternal smoking status during early pregnancy and fetal growth. Birth weight was estimated using the least-squares method after controlling for covariates.

Results

After controlling for potential confounding factors, maternal smoking status during pregnancy was significantly associated with birth weight. There was a significant difference in birth weight between NS and SM for both male and female infants (male infants, 3096.2 g [NS] vs 2959.8 g [SM], P < 0.001; female infants, 3018.2 g [NS] vs 2893.7 g [SM], P < 0.001).

Conclusions

Using data from a large nationwide birth cohort study in Japan, we have shown that maternal smoking during pregnancy may reduce birth weight by 125–136 g.

'Only Fathers Smoking' Contributes the Most to Socioeconomic Inequalities: Changes in Socioeconomic Inequalities in Infants' Exposure to Second Hand Smoke over Time in Japan

BACKGROUND

Exposure to second hand smoke (SHS) is one of the major causes of premature death and disease among children. While socioeconomic inequalities exist for adult smoking, such evidence is limited for SHS exposure in children. Thus, this study examined changes over time in socioeconomic inequalities in infants' SHS exposure in Japan.

METHODS

This is a repeated cross-sectional study of 41,833 infants born in 2001 and 32,120 infants born in 2010 in Japan from nationally representative surveys using questionnaires. The prevalence of infants' SHS exposure was determined and related to household income and parental education level. The magnitudes of income and educational inequalities in infants' SHS exposure were estimated in 2001 and 2010 using both absolute and relative inequality indices.

RESULTS

The prevalence of SHS exposure in infants declined from 2001 to 2010. The relative index of inequality increased from 0.85 (95% confidence interval [CI], 0.80 to 0.89) to 1.47 (95% CI, 1.37 to 1.56) based on income and from 1.22 (95% CI, 1.17 to 1.26) to 2.09 (95% CI, 2.00 to 2.17) based on education. In contrast, the slope index of inequality decreased from 30.9 (95% CI, 29.3 to 32.6) to 20.1 (95% CI, 18.7 to 21.5) based on income and from 44.6 (95% CI, 43.1 to 46.2) to 28.7 (95% CI, 27.3 to 30.0) based on education. Having only a father who smoked indoors was a major contributor to absolute income inequality in infants' SHS exposure in 2010, which increased in importance from 45.1% in 2001 to 67.0% in 2010.

CONCLUSIONS

The socioeconomic inequalities in infants' second hand smoke exposure increased in relative terms but decreased in absolute terms from 2001 to 2010. Further efforts are needed to encourage parents to quit smoking and protect infants from second hand smoke exposure, especially in low socioeconomic households that include non-smoking mothers.

Childbirth expense support and small-for-gestational-age infants in Japan

BACKGROUND

Poor nutritional status during the fetal period could cause perinatal and lifelong health disadvantages in neonates. The aim of this study was to investigate the background of pregnant women receiving childbirth expense support (CES), pregnancy outcome, and neonatal anthropometric data.

METHODS

A retrospective cohort study was conducted using 823 antenatal and delivery records in a perinatal center located in one of the poorest areas in Japan. Neonates who were small for gestational age (SGA) were compared between the CES and the non-CES groups.

RESULTS

The incidences of low birthweight (LBW) and SGA were significantly higher in the group receiving CES (14.6% and 14.6%, respectively). The adjusted OR of CES was 2.78 (95%CI: 1.32-5.87) and the adjusted OR of maternal smoking was 5.03 (95%CI: 2.74-9.21), indicating that CES and maternal smoking were directly associated with SGA.

CONCLUSIONS

CES recipients had a higher prevalence of SGA infants. CES was independently associated with SGA. Previous studies have shown that smoking is a major risk factor for SGA. Further studies are needed to identify risk factors of SGA specific to CES recipients.

Joint Effects of Structural Racism and Income Inequality on Small-for-Gestational-Age Birth

OBJECTIVES

We examined potential synergistic effects of racial and socioeconomic inequality associated with small-for-gestational-age (SGA) birth.

METHODS

Electronic medical records from singleton births to White and Black women in 10 US states and the District of Columbia (n = 121 758) were linked to state-level indicators of structural racism, including the ratios of Blacks to Whites who were employed, were incarcerated, and had a bachelor's or higher degree. We used state-level Gini coefficients to assess income inequality. Generalized estimating equations models were used to quantify the adjusted odds of SGA birth associated with each indicator and the joint effects of structural racism and income inequality.

RESULTS

Structural racism indicators were associated with higher odds of SGA birth, and similar effects were observed for both races. The joint effects of racial and income inequality were significantly associated with SGA birth only when levels of both were high; in areas with high inequality levels, adjusted odds ratios ranged from 1.81 to 2.11 for the 3 structural racism indicators.

CONCLUSIONS

High levels of racial inequality and socioeconomic inequality appear to increase the risk of SGA birth, particularly when they co-occur.

Are secondhand smoke-related diseases of children associated with parental smoking cessation? Determinants of parental smoking cessation in a population-based cohort study

OBJECTIVE

Little is known about whether secondhand smoke (SHS)-related diseases of young children, such as asthma, induce parental smoking cessation during the early child-rearing period. Our objective was therefore to show the association in addition to other potential determinants of parental cessation.

METHODS

We analyzed data from the Longitudinal Survey of Newborns in the 21st Century in Japan, from 0.5years (N=47,015) to 4.5years (N=39,817), having selected participants whose parents smoked at baseline (maternal smoking N=8,037; paternal smoking N=28,486). Multivariable log-binomial regression models were used to calculate the prevalence ratios for parental smoking cessation according to the onset of SHS-related diseases of their children, using inverse probability weight to account for non-response at follow-up.

RESULTS

A total of 16.7% of smoking mothers and 14.5% of smoking fathers had stopped smoking at follow-up. The onset of SHS-related children's diseases was not statistically significantly associated with either maternal or paternal smoking cessation after multivariable adjustments. Strong determinants were, for example, number of cigarettes smoked per day and partner's smoking status during follow-up.

CONCLUSION

SHS-related children's diseases were not associated with parental smoking cessation. It may therefore be necessary to provide additional support for parental smoking cessation within their child's medical care setting.

Maternal and paternal indoor or outdoor smoking and the risk of asthma in their children: a nationwide prospective birth cohort study

BACKGROUND

Little is known about the differential impact of combinations of parental smoking behavior (indoor or outdoor smoking, or not smoking) on preventing childhood asthma. Our objective was to examine the association between parental smoking behavior and children's asthma.

METHODS

A nationally representative population-based birth cohort of 40,580 babies, aged 0.5 years in 2001 (response rate, 87.8%), was studied to estimate adjusted odds ratios of combinations of maternal and paternal indoor or outdoor smoking at home for physician visits and hospitalization for childhood asthma up to 8-years-old, and population attributable fractions.

RESULTS

Odds of hospitalization for asthma among children whose father alone smokes indoors at home did not largely increase (up to 20%). However, if the mother also smokes indoors at home, the odds strongly increased. After adjusting for demographic, perinatal and socioeconomic factors, the increase in odds for children whose father and mother both smoke indoors compared to children with non-smoking parents was 54% (95% confidence interval: 21-96%), 43% (8-90%) and 72% (22-143%) for children aged 0.5<-2.5, 2.5<-4.5 and 4.5<-8 years-old, respectively. The odds ratios of smoking outdoors did not largely differ from those of smoking indoors. Our estimation of population attributable fractions revealed that if all parents in Japan quit smoking, hospitalization of children for asthma could be reduced by 8.3% (2.2-14.3%), 9.3% (0.9-17.6%) and 18.2% (7.7-28.8%), respectively.

CONCLUSIONS

Parental indoor smoking at home increased and exacerbated children's asthma. Smoking at home, whether it is indoors or outdoors, may increase the risks for asthma attacks of their children.