Social trends in singleton births and birth weight in Wirral residents, 1990-2001

Birthweights at term have increased globally: insights from a systematic review of 183 million births

OBJECTIVE

This study aimed to assess global trends in mean birthweights at term, as reported in peer-reviewed literature.

DATA SOURCES

We electronically searched PubMed, Embase, and Web of Science up to September 2023, using combinations of the search terms: "birth weight"; "birth-weight"; "birthweight"; "trend". There were no restrictions based on language or geographic area.

STUDY ELIGIBILITY CRITERIA

We included all ecological and observational studies reporting mean birthweight at term as a continuous numerical variable over time.

METHODS

We assessed the quality of included studies using the Dufault and Klar checklist modified by Betran et al. Univariate and multivariate linear models were used to examine the effects of time (years) and geographical origins. Subgroup analyses focused on national data sources and on data collected from 1950 onward.

RESULTS

Among 6447 reviewed articles, 29 met our criteria, reporting mean birthweight data from over 183 million infants worldwide. Most studies were hospital-based (48.3%), 44.8% used national data, and a minority used municipality, community, or regional data (6.9%). Geographically, North America (31.0%) had the highest representation, followed by Asia and Europe (27.6% each), and South America and Oceania (6.9% each). Our univariate linear regression model (Model 1) revealed a significant increase in mean birthweight at term over time (4.74 g/y; 95% confidence interval, 3.95-5.53; P<.001). Model 2, incorporating continental dummy variables into the first model, confirmed this trend (3.85 g/y; 95% confidence interval, 2.96-4.74; P<.001). Model 3, focusing on available national data, did not find a significant relationship. Model 4 narrowed its focus on records from 1950 onward, reporting a robust annual increase of 7.26 g/y (95% confidence interval, 6.19-8.33; P<.001). Model 5, adjusting for the number of participants included in each study, reported a conclusive mean term birthweight increase of 1.46 g/y (95% confidence interval, 0.74-2.18; P<.001).

CONCLUSION

This systematic review of 29 studies shows an increase in term birthweights over time, particularly when considering data since 1950. Limitations include study quality variations, data source diversity, and data sparsity, underscoring the need for future research to use precise gestational age distinctions and predetermined time frames to gain a deeper understanding of this trend and its implications for maternal and child health.

Adverse neonatal outcomes and house prices in London

Objective To explore whether the average price of houses per postcode sector [sector house average prices (SHAP)] is related to perinatal outcomes and whether gestational age would be lower and mortality higher in the least expensive areas compared to the most expensive. Methods All neonatal unit admissions at King's College Hospital from 1/1/2012 to 31/12/2016 were reviewed. The SHAP was retrieved from the Land Registry and the population was divided in equal quintiles with quintiles 1 and 5 representing the most and least expensive areas, respectively. Gestational age and birth weight z-score were collected. Mortality was defined as death before discharge from neonatal care. Results Three thousand three hundred and sixty infants were included and divided in quintiles consisting of 672 infants. Gestational age was lower in quintile 5 compared to all other quintiles (adjusted P<0.001). Birthweight z-score was not significantly different between the quintiles. The SHAP was lower in the infants who died before discharge (n=92) compared to the SHAP of the infants who were alive at discharge (n=3268) (P<0.001). Infants of quintile 5 had 6 times higher risk of death before discharge from neonatal care compared to infants of quintile 1. Conclusion Low SHAPs were associated with poorer perinatal outcomes suggesting SHAP could potentially be used in perinatal populations to determine socio-economic status and associated outcomes.

Does area deprivation modify the association between exposure to a nitrate and low-dose atrazine metabolite mixture in drinking water and small for gestational age? A historic cohort study

Birth weight may be influenced by environmental and socio-economic factors that could interact. The main objective of our research was to investigate whether area deprivation may modify the association between drinking water exposure to a mixture of atrazine metabolites and nitrates during the second trimester of pregnancy and prevalence of small for gestational age (SGA) neonates. We conducted a historic cohort study in Deux-Sèvres, France between 2005 and 2010, using birth records, population census and regularly performed drinking water withdrawals at community water systems. Exposure to an atrazine metabolite/nitrate mixture in drinking water was divided into six classes according to the presence or absence of atrazine metabolites and to the terciles of nitrate concentrations in each trimester of pregnancy. We used a logistic regression to model the association between SGA and mixture exposure at the second trimester while taking into account the area deprivation measured by the Townsend index as an effect modifier and controlling for the usual confounders. We included 10,784 woman-neonate couples. The risk of SGA when exposed to second tercile of nitrate without atrazine metabolites was significantly greater in women living in less deprived areas (OR = 2.99; 95 % CI (1.14, 7.89)), whereas it was not significant in moderately and more deprived areas. One of the arguments used to explain this result is the presence of competing risk factors in poorer districts.

The social determinants of infant mortality and birth outcomes in Western developed nations: a cross-country systematic review

Infant mortality (IM) and birth outcomes, key population health indicators, have lifelong implications for individuals, and are unequally distributed globally. Even among western industrialized nations, striking cross-country and within-country patterns are evident. We sought to better understand these variations across and within the United States of America (USA) and Western Europe (WE), by conceptualizing a social determinants of IM/birth outcomes framework, and systematically reviewing the empirical literature on hypothesized social determinants (e.g., social policies, neighbourhood deprivation, individual socioeconomic status (SES)) and intermediary determinants (e.g., health behaviours). To date, the evidence suggests that income inequality and social policies (e.g., maternal leave policies) may help to explain cross-country variations in IM/birth outcomes. Within countries, the evidence also supports neighbourhood SES (USA, WE) and income inequality (USA) as social determinants. By contrast, within-country social cohesion/social capital has been underexplored. At the individual level, mixed associations have been found between individual SES, race/ethnicity, and selected intermediary factors (e.g., psychosocial factors) with IM/birth outcomes. Meanwhile, this review identifies several methodological gaps, including the underuse of prospective designs and the presence of residual confounding in a number of studies. Ultimately, addressing such gaps including through novel approaches to strengthen causal inference and implementing both health and non-health policies may reduce inequities in IM/birth outcomes across the western developed world.

Social inequality and infant health in the UK: systematic review and meta-analyses

OBJECTIVES

To determine the association between area and individual measures of social disadvantage and infant health in the UK.

DESIGN

Systematic review and meta-analyses.

DATA SOURCES

26 databases and websites, reference lists, experts in the field and hand-searching.

STUDY SELECTION

36 prospective and retrospective observational studies with socioeconomic data and health outcomes for infants in the UK, published from 1994 to May 2011.

DATA EXTRACTION AND SYNTHESIS

2 independent reviewers assessed the methodological quality of the studies and abstracted data. Where possible, study outcomes were reported as ORs for the highest versus the lowest deprivation quintile.

RESULTS

In relation to the highest versus lowest area deprivation quintiles, the odds of adverse birth outcomes were 1.81 (95% CI 1.71 to 1.92) for low birth weight, 1.67 (95% CI 1.42 to 1.96) for premature birth and 1.54 (95% CI 1.39 to 1.72) for stillbirth. For infant mortality rates, the ORs were 1.72 (95% CI 1.37 to 2.15) overall, 1.61 (95% CI 1.08 to 2.39) for neonatal and 2.31 (95% CI 2.03 to 2.64) for post-neonatal mortality. For lowest versus highest social class, the odds were 1.79 (95% CI 1.43 to 2.24) for low birth weight, 1.52 (95% CI 1.44 to 1.61) for overall infant mortality, 1.42 (95% CI 1.33 to1.51) for neonatal and 1.69 (95% CI 1.53 to 1.87) for post-neonatal mortality. There are similar patterns for other infant health outcomes with the possible exception of failure to thrive, where there is no clear association.

CONCLUSIONS

This review quantifies the influence of social disadvantage on infant outcomes in the UK. The magnitude of effect is similar across a range of area and individual deprivation measures and birth and mortality outcomes. Further research should explore the factors that are more proximal to mothers and infants, to help throw light on the most appropriate times to provide support and the form(s) that this support should take.

Are there differences in birth weight between neighbourhoods in a Nordic welfare state?

Background

The objective of this cohort study was to examine the effect on birth weight of living in a disadvantaged neighbourhood in a Nordic welfare state. Birth weight is a health indicator known to be sensitive to political and welfare state conditions. No former studies on urban neighbourhood differences regarding mean birth weight have been carried out in a Nordic country.

Methods

A register based on individual data on children's birth weight and maternal risk factors was used. A neighbourhood characteristic, i.e. an aggregated measure on income was also included. Connections between individual- and neighbourhood-level determinants and the outcome were analysed using multi-level regression technique. The study covered six hundred and ninety-six neighbourhoods in the three major cities of Sweden, Stockholm, Göteborg and Malmö, during 1992–2001. The majority of neighbourhoods had a population of 4 000–10 000 inhabitants. An average of 500 births per neighbourhood were analysed in this study.

Results

Differences in mean birth weight in Swedish urban neighbourhoods were minor. However, gestational length, parity and maternal smoking acted as modifiers of the neighbourhood effects. Most of the observed variation in mean birth weight was explained by individual risk factors.

Conclusion

Welfare institutions and benefits in Sweden might buffer against negative infant outcomes due to adverse structural organisation of urban neighbourhoods.

Social deprivation and outcomes in colorectal cancer

Background

The aim of this study was to examine the influence of social deprivation on postoperative mortality and length of stay in patients having surgery for colorectal cancer.

Methods

Data were extracted from the Association of Coloproctology of Great Britain and Ireland database of patients presenting between April 2001 and March 2002. The effect of social deprivation, measured by the Townsend score, on 30-day postoperative mortality and length of stay was evaluated by two-level hierarchical regression analysis.

Results

A total of 7290 (86·8 per cent) patients underwent surgery. Operative mortality was 6·7 per cent and median length of stay 11 days. Deprivation indices were significantly higher in patients with Dukes' ‘D’ cancers, undergoing emergency surgery and with higher American Society of Anesthesiologists (ASA) grades (P &lt; 0·005). Worsening deprivation was associated with higher operative mortality and longer stay (P = 0·014). For each unit increase in deprivation, there was 2·9 (95 per cent confidence interval 0·5 to 5·2) per cent increase in 30-day mortality. On multifactorial analysis, social deprivation was an independent predictor of length of stay, but its effect on operative mortality was explained by differences in ASA grade, operative urgency and Dukes' classification.

Conclusion

Social deprivation was an independent risk factor of postoperative length of stay and associated with higher postoperative mortality. These results have important implications for risk modelling of postoperative outcomes.

Social deprivation and admission for neonatal care

OBJECTIVE

To determine whether social deprivation is associated with neonatal unit admission.

SETTING

English district general hospital.

METHOD

Retrospective review of neonatal unit admission records between 1990 and 2002.

RESULTS

There was a linear increase in admission rates with increasing deprivation. The admission rate was 6.1% of live births for infants in the most affluent quartile compared with 11.1% for those in the most deprived quartile. Admission rates for all indications except jaundice and feeding problems increased with increasing deprivation.

CONCLUSION

Social deprivation correlates strongly with neonatal morbidity and the need for neonatal unit admission. This finding has implications for professionals in public health and primary and secondary care.

Is the rate of biological aging, as measured by age at diagnosis of cancer, socioeconomically patterned?

STUDY OBJECTIVE

To investigate the hypothesis that biological aging, as measured by age at diagnosis of some common cancers, is socioeconomically patterned.

DESIGN

A cross sectional analysis of the association between an area based measure of material deprivation and age at diagnosis of four common cancers (breast, prostate, colorectal, and lung cancers). A further analysis, restricted to breast and colorectal cancer, adjusted for stage and grade of cancer at diagnosis.

SETTING

The Northern and Yorkshire cancer registry and information service, Northern and Yorkshire region, UK.

PARTICIPANTS

All people living in the Northern and Yorkshire region diagnosed with breast, prostate, colorectal, or lung cancer in 1986-1995. All people living in the Northern and Yorkshire region diagnosed with breast or colorectal cancer in 1998-2000 with data on stage and grade of cancer at diagnosis.

MAIN RESULTS

There was evidence that greater material deprivation was associated with younger age at diagnosis of cancer in prostate (beta coefficient -0.073), colorectal (women: -0.042; men: -0.063), and lung cancer (women: -0.214; men: -0.161). The opposite association was found in women with breast cancer (0.149). Adjusting for stage and grade at incidence, where possible, had little effect on the magnitude of the beta coefficients.

CONCLUSIONS

Age at diagnosis of some common cancers seems to be socioeconomically patterned with people from more deprived areas being diagnosed with prostate, colorectal, and lung cancers earlier in life. The opposite was seen in women with breast cancer. Further work is required to investigate the socioeconomic distribution of more accurate measures of biological aging.