Which factors could explain the low birth weight paradox?

Urban social environment and low birth weight in 360 Latin American cities

OBJECTIVE

Using data compiled by the SALURBAL project (Urban Health in Latin America; 'Salud Urbana en América Latina') we quantified variability in low birth weight (LBW) across cities in Latin America, and evaluated the associations of socio-economic characteristics at various levels (maternal, sub-city and city) with the prevalence of LBW.

METHODS

The sample included 8 countries, 360 cities, 1321 administrative areas within cities (sub-city units) and birth registers of more than 4.5 million births for the year 2014. We linked maternal education from birth registers to data on socioeconomic characteristics of sub-cities and cities using the closest available national population census in each country. We applied linear and Poisson random-intercept multilevel models for aggregated data.

RESULTS

The median prevalence of city LBW by country ranged from a high of 13% in Guatemala to a low of 5% in Peru (median across all cities was 7.8%). Most of the LBW variability across sub-cities was between countries, but there were also significant proportions between cities within a country, and within cities. Low maternal education was associated with higher prevalence of LBW (Prevalence rate ratios (PRR) for less than primary vs. completed secondary or more 1.12 95% CI 1.10, 1.13) in the fully adjusted model. In contrast, higher sub-city education and a better city social environment index were independently associated with higher LBW prevalence after adjustment for maternal education and age, city population size and city gross domestic product (PRR 1.04 95% CI 1.03, 1.04 per SD higher sub-city education and PRR 1.02 95% CI 1.00, 1.04 per SD higher SEI). Larger city size was associated with a higher prevalence of LBW (PRR 1.06; 95% CI 1.01, 1.12).

CONCLUSION

Our findings highlight the presence of heterogeneity in the distribution of LBW and the importance of maternal education, local and broader social environments in shaping LBW in urban settings of Latin America. Implementing context-sensitive interventions guided to improve women's education is recommended to tackle LBW in the region.

Low birth weight trends in Organisation for Economic Co-operation and Development countries, 2000-2015: economic, health system and demographic conditionings

BACKGROUND

Low birth weight rates are increasing in both developed and developing countries. Although several maternal factors have been identified as associated with low birth weight, little is known of economic or organization factors influencing this increase. This study aims to ascertain the twenty-first century relationships between the contextual country factors and low birth weight rates.

METHODS

We analyse trends of low birth weight rates in Organisation for Economic Co-operation and Development (OECD) countries. Data from 2000 to 2015 were obtained from the OECD data base. Their relationships with demographic and economic variables, health habits, woman-related preventive measures, health care system organization and funding, health care work force and obstetric care were analysed using random-effects linear regression.

RESULTS

Low birth weight rates are higher in Southern Europe (7.61%) and lower in Northern Europe (4.68%). Low birth weight rates escalated about 20% in Southern Europe and to less extent in Easter Europe (7%) and Asian/Oceanian countries, while remained stable in America, Central Europe and Northern Europe. Investment in health care, private health system coverage, ratios of paediatricians and obstetricians, average length of admission due to pregnancy or birth and Caesarean section rate were associated with higher low birth weight rates. Factors associated with lower low birth weight rates were health care coverage, public health system coverage, hospitals per million inhabitants, and ratios of health care workers, physicians, midwives and nurses.

CONCLUSIONS

In OECD countries, LBW rates are related to contextual country characteristics such as GDP per capita, which is inversely related to LBW rate. Health care system factors, including health care coverage or investment in public health system, are directly associated with lower LBW rates.

Maternal Active Smoking During Pregnancy and Low Birth Weight in the Americas: A Systematic Review and Meta-analysis

Introduction

Smoking during pregnancy may negatively impact newborn birth weight. This study investigates the relationship between maternal active smoking during pregnancy and low birth weight in the Americas through systematic review and meta-analysis.

Methods

A literature search was conducted through indexed databases and the grey literature. Case-control and cohort studies published between 1984 and 2016 conducted within the Americas were included without restriction regarding publication language. The article selection process and data extraction were performed by two independent investigators. A meta-analysis of random effects was conducted, and possible causes of between-study heterogeneity were evaluated by meta-regressions and subgroup analyses. Publication bias was assessed by visual inspection of Begg's funnel plot and by Egger's regression test.

Results

The literature search yielded 848 articles from which 34 studies were selected for systematic review and 30 for meta-analysis. Active maternal smoking was associated with low birth weight, OR = 2.00 (95% CI: 1.77-2.26; I2 = 66.3%). The funnel plot and Egger's test (p = .14) indicated no publication bias. Meta-regression revealed that sample size, study quality, and the number of confounders in the original studies did not account for the between-study heterogeneity. Subgroup analysis indicated no significant differences when studies were compared by design, sample size, and regions of the Americas.

Conclusion

Low birth weight is associated with maternal active smoking during pregnancy regardless of the region in the Americas or the studies' methodological aspects.

Implications

A previous search of the major electronic databases revealed that no studies appear to have been conducted to summarize the association between maternal active smoking during pregnancy and low birth weight within the Americas. Therefore, this systematic review may help to fill the information gap. The region of the Americas contains some of the most populous countries in the world; therefore, this study may provide useful data from this massive segment of the world's population.

Changes in perinatal health in two birth cohorts (1997/1998 and 2010) in São Luís, Maranhão State, Brazil

The objective of this study was to analyze changes in perinatal health in two birth cohorts started in 1997/1998 and 2010, respectively, in São Luís, Maranhão State, Brazil. A total of 2,493 live born infants were included in 1997/1998 and 5,166 in 2010. Low birth weight (LBW) rate did not change (8.5% in 1997/1998 and 8.6% in 2010). Preterm birth (PTB) rate also remained stable (13.2% in 1997/1998 and 13% in 2010). Teenage deliveries and births to single mothers decreased. Maternal schooling and prenatal care coverage increased. Intrauterine growth restriction (IUGR) decreased from 13.3% to 10.6% (p < 0.001). The perinatal mortality rate decreased from 36.6 to 20.7 per 1,000 (p < 0.001) and the infant mortality rate (IMR) dropped from 28.5 to 12.8 per 1,000 (p < 0.001). The cesarean rate increased from 34.1% to 47.5% (p < 0.001). In conclusion, despite favorable changes in socio-demographic, behavioral, and health service factors and decreasing rates of IUGR and perinatal and infant mortality, LBW and PTB remained stable, while the cesarean rate increased.

Escolha da via de parto pela mulher: autonomia ou indução?

Este estudo teve como objetivo conhecer a percepção e preferência de gestantes e puérperas sobre o parto vaginal e cesáreo. Pesquisa transversal, de caráter exploratório, com abordagem quanti-qualitativa, ocorrida em quatro Unidades Básicas de Saúde (UBSs) de um município de pequeno porte do Vale do Taquari. A amostra foi composta por 81 gestantes, o que significa 20,88% dos nascimentos anuais, e 28,72% das gestantes cadastradas no Sistema de Informações do Programa de Humanização do Pré-Natal e Nascimento do Ministério da Saúde (SISPRENATAL); destas, 75% (n=61) preferem o parto vaginal e 25% (n=20), o parto abdominal. Estes dados indicam que a preferência referida pelas gestantes não influencia no tipo de parto realizado, pois o índice de cesáreas do município em questão é de 89%. Foram entrevistadas três puérperas que realizaram partos abdominais e na concepção destas o parto vaginal oferece mais risco na parturição. Conclui-se que a humanização da atenção no pré-natal e ao parto, com indicação médica baseada em evidências, pode contribuir para a redução do percentual de cesarianas, pois o estudo mostra que estas não têm ocorrido, na maioria das vezes, por escolha da mulher.

Is adolescent pregnancy a risk factor for low birth weight?

OBJECTIVE

The objective of this study was to evaluate whether adolescent pregnancy is a risk factor for low birth weight (LBW) babies.

METHODS

This was a cross-sectional study of mothers and their newborns from a birth cohort in Aracaju, Northeastern Brazil. Data were collected consecutively from March to July 2005. Information collected included socioeconomic, biological and reproductive aspects of the mothers, using a standardized questionnaire. The impact of early pregnancy on birth weight was evaluated by multiple logistic regression.

RESULTS

We studied 4,746 pairs of mothers and their babies. Of these, 20.6% were adolescents (< 20 years of age). Adolescent mothers had worse socioeconomic and reproductive conditions and perinatal outcomes when compared to other age groups. Having no prenatal care and smoking during pregnancy were the risk factors associated with low birth weight. Adolescent pregnancy, when linked to marital status "without partner", was associated with an increased proportion of low birth weight babies.

CONCLUSIONS

Adolescence was a risk factor for LBW only for mothers without partners. Smoking during pregnancy and lack of prenatal care were considered to be independent risk factors for LBW.

Reflexões sobre o excesso de cesarianas no Brasil e a autonomia das mulheres

A medicalização do parto, como resultado da medicalização social, tem sido descrita como um processo sociocultural complexo que transforma em necessidades médicas, vivências, sofrimentos e dores antes administradas no próprio ambiente familiar ou comunitário. O objetivo é refletir sobre o excesso de cesarianas no Brasil, em uma perspectiva crítica e propositiva. Dados sobre taxas de cesariana e estudos sobre a preferência das mulheres sobre a via de parto são discutidos com a finalidade de contribuir para o debate sobre autonomia das usuárias do sistema de saúde. A medicalização é uma transformação cultural que influenciou a capacidade de enfrentamento autônomo da experiência de parir, visto que implica em dependência excessiva, heteronomia e consumo abusivo de cesarianas. Além disso, discutem-se as redes e os movimentos sociais como possíveis facilitadores da autonomia das mulheres, na medida em que possibilitam apoio mútuo e compartilhamento de experiências, contribuindo para a construção de relações mais igualitárias entre as mulheres e os profissionais de saúde. A participação nessas redes possibilita a mobilização coletiva das mulheres no sentido de reivindicarem seus direitos junto às diversas instâncias da sociedade.

The impact of perinatal and socioeconomic factors on mental health problems of children from a poor Brazilian city: a longitudinal study

BACKGROUND

Low birth weight and preterm birth, and social disadvantage may negatively affect mental health of children, but findings have been inconsistent.

OBJECTIVES

To assess the influence of perinatal and social factors on mental health problems in children aged 7-9 years.

METHODS

A random sample of 805 births in São Luís, Brazil was studied in 1997/1998 and again in 2005/2006. Perinatal, socioeconomic and demographic variables were assessed within 24 h after delivery. The Strengths and Difficulties Questionnaire (SDQ) was used to assess mental health problems in the children. Simple and multiple Poisson regressions were used for statistical analysis.

RESULTS

The overall prevalence of mental health problems in the total sample was 47.7%. The prevalences of emotional and conduct problems were 58.2 and 48.8%, respectively. Only paternal age (<20 years) was associated with mental health problems as measured by the full SDQ scale (prevalence ratio PR = 1.27). Children born to single mothers (PR = 1.31) and those with birth weight from 1,500 to 2,499 g (PR = 1.18) and from 2,500 to 2,999 g (PR = 1.17) had a higher risk of emotional problems, but those from low income families had a lower risk (PR = 0.80). Children with a father of less than 20 years had a higher risk of having problems with their peers (PR = 1.75). A maternal education of 9 years or over was inversely associated with peer (PR = 0.70) and conduct problems (PR = 0.73). Girls had a lower risk of conduct (PR = 0.77) and hyperactivity problems (PR = 0.68). A maternal education of 4 years or less increased the risk of hyperactivity (PR = 1.48).

CONCLUSIONS

Socioeconomic and demographic conditions were better predictors of mental health problems in children than birth weight or preterm birth. However, since most effect sizes were small most mental health problems were, unexplained by the variables in the study.

The epidemiologic paradox of low birth weight in Brazil

OBJECTIVE

To examine whether the low birth weight (LBW) paradox exists in Brazil.

METHODS

LBW and cesarean section rates between 1995 and 2007 were estimated based on data from SINASC (Brazilian Live Births Database). Infant mortality rates (IMRs) were obtained using an indirect method that correct for underreporting. Schooling information was obtained from census data. Trends in LBW rate were assessed using joinpoint regression models. The correlations between LBW rate and other indicators were graphically assessed by lowess regression and tested using Spearman's rank correlation.

RESULTS

In Brazil, LBW rate trends were non-linear and non-significant: the rate dropped from 7.9% in 1995 to 7.7% in 2000, then increased to 8.2% in 2003 and remained nearly steady thereafter at 8.2% in 2007. However, trends varied among Brazilian regions: there were significant increases in the North from 1999 to 2003 (2.7% per year), and in the South (1.0% per year) and Central-West regions (0.6% per year) from 1995 to 2007. For the entire period studied, higher LBW and lower IMRs were seen in more developed compared to less developed regions. In Brazilian States, in 2005, the higher the IMR rate, the lower the LBW rate (p=0.009); the lower the low schooling rate, the lower the LBW rate (p=0.007); the higher the number of neonatal intensive care beds per 1,000 live births, the higher the LBW rate (p=0.036).

CONCLUSIONS

The low birth weight paradox was seen in Brazil. LBW rate is increasing in some Brazilian regions. Regional differences in LBW rate seem to be more associated to availability of perinatal care services than underlying social conditions.

SECULAR TREND OF VERY LOW BIRTH WEIGHT RATE IN PORTO ALEGRE, SOUTHERN BRAZIL

The strong association of very low birth weight (VLBW; <1500 g) with infant mortality is well known. There are no data related to VLBW trends in Brazil although findings from some large surveys carried out in small- and medium-sized cities have demonstrated an increase in low birth weight (LBW; <2500 g) rates over the last 30 years. The aim of this study was to evaluate the secular trend of VLBW in the city of Porto Alegre, a large city in a developed area in southern Brazil, and the potential determinants of this trend during the 1990s and early 2000s. This is a registry-based study. Data were obtained from birth certificates of all live births in the city from 1994 to 2005. The variables analysed were: VLBW as the dependent variable and maternal age and schooling, type of delivery, type of hospital, number of live births, gestational age, newborn gender and unemployment rate. The incidence ratio rate (IRR) using Poisson regression was calculated to identify possible trends in VLBW rates. Poisson regressions were performed in order to assess the influence of some independent variables on VLBW. A total of 257,740 singleton newborns were delivered in the city during the period, with a steady reduction in the total number of live births per year from 23,296 in 1994 to 18,325 in 2005. The results showed a small but significant increase in VLBW (p for trend=0.049). There was a significant trend towards adequacy for gestational age per birth weight, suggesting a reduction in rates of intrauterine growth restriction (IUGR) (p<0.001). The findings showed a significant increase of 1% per year in the probability of VLBW. The main risk factors were related to VLBW mothers with low levels of schooling, public hospitals and multiparity and nulliparity. After adjustment, nulliparity remained as a significant risk factor. The interaction between type of hospital and type of delivery indicated that the probability for VLBW was 3.6 times higher (p<0.001) among those born in public hospitals by Caesarean section than those born in private hospitals by vaginal delivery. The results show that southern Brazil is going through a demographic transition characterized by a significant decrease in number of live births associated with a small increase in VLBW rates, a decrease in IUGR rates and stabilization of LBW.

Características das gestações, partos e recém-nascidos da região metropolitana de Aracaju, Sergipe, Brasil

OBJETIVOS: descrever as características das gestações, partos e nascimentos da região metropolitana de Aracaju. As principais características demográficas e socioeconômicas e de atenção à saúde da população foram avaliadas. MÉTODOS: estudo transversal dos nascimentos ocorridos entre março e julho de 2005, procedentes da região metropolitana de Aracaju, Sergipe, Brasil. Todas as mães que tiveram parto único nascido vivo foram entrevistadas através de um questionário estruturado, com informações sobre as condições demográficas, socioeconômicas, história sexual/reprodutiva. Registros do peso, comprimento e perímetro cefálico das crianças foram transferidos para o questionário. Foi feita comparação com outros estudos brasileiros de características semelhantes. RESULTADOS: foram analisados 4746 nascimentos de parto único de Aracaju, com 69% das mães referindo renda inferior a três salários mínimos. As mães adolescentes representaram 20,6% da amostra. Entre todos os nascimentos, 7,7% tiveram duração inferior a 37 semanas, percentual semelhante ao de baixo peso ao nascer (7,2%). Prevaleceu a assistência pré-natal oferecida pelo Sistema Único de Saúde (SUS) (76,0%), que custeou 85,2% dos partos. Destes, 31,6% foram cesáreas. CONCLUSÕES: o estudo mostrou menores percentuais de partos cesária, prematuridade e baixo peso ao nascer que os encontrados em Ribeirão Preto, São Luís e Pelotas. Estudos como este podem ser muito úteis ao planejamento de saúde perinatal.