Why are the low birthweight rates in Brazil higher in richer than in poorer municipalities? Exploring the epidemiological paradox of low birthweight

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.

Factors associated with low birth weight at term: a population-based linkage study of the 100 million Brazilian cohort

BACKGROUND

Factors associated with low birth weight at term (TLBW), a proxy for intrauterine growth restriction (IUGR), are not well-elucidated in socioeconomically vulnerable populations. This study aimed to identify the factors associated with TLBW in impoverished Brazilian women.

METHODS

Records in the 100 Million Brazilian Cohort database were linked to those in the National System of Information on Live Births (SINASC) to obtain obstetric, maternal, birth and socioeconomic data between 2001 and 2015. Multivariate logistic regression was performed to investigate associations between variables of exposure and TLBW.

RESULTS

Of 8,768,930 term live births analyzed, 3.7% presented TLBW. The highest odds of TLBW were associated with female newborns (OR: 1.49; 95% CI: 1.47-1.50), whose mothers were black (OR: 1.20; 95% CI: 1.18-1.22), had a low educational level (OR: 1.57; 95% CI: 1.53-1.62), were aged ≥35 years (OR: 1.44; 95% CI: 1.43-1.46), had a low number of prenatal care visits (OR: 2.48; 95% CI: 2.42-2.54) and were primiparous (OR: 1.62; 95% CI: 1.60-1.64). Lower odds of TLBW were found among infants whose mothers lived in the North, Northeast and Center-West regions of Brazil compared to those in the South.

CONCLUSION

Multiple aspects were associated with TLBW, highlighting the need to comprehensively examine the mechanisms underlying these factors, especially in more vulnerable Brazilian populations, in order to contribute to the elaboration of health policies and promote better conditions of life for poor and extremely poor mothers and children.

[Full-term low birth weight and its relationship with the socioeconomic conditions of municipalities in Antioquia: Spatio-temporal analysis]

INTRODUCTION

Low birth weight is one of the main health predictors for childhood and adulthood. It is highly prevalent in developing countries and in children from poorer social classes.

OBJECTIVE

To analyze the geographical distribution and the trends of full-term low birth weight in the 125 municipalities of the department of Antioquia and their association with the socioeconomic conditions of the municipalities between 2000 and 2014.

MATERIALS AND METHODS

We conducted a longitudinal ecological study. The dependent variable was the prevalence of full-term low birth weight in 125 municipalities. The socioeconomic conditions of the municipalities were evaluated using the Human Development Index and the unsatisfied basic needs index.

RESULTS

Between 2000 and 2014, the prevalence of full-term low birth weight in Antioquia was 2.7 per 100 live births; this prevalence decreased steadily over time. This trend was also observed between regions, with the exception of the Occidente and Urabá regions, which showed increases of approximately 20.0%. The results also showed a reduction in geographical differences between the 125 municipalities, with the coefficient of variation decreasing from 20.6% to 13.72% over the 14-yearperiod. Finally, we found a positive social gradient between the full-term low birth weight prevalence and the level of development in the municipalities.

CONCLUSION

Full-term low birth weight prevalence decreased between 2000 and 2014, with some regions showing greater reductions than others. Paradoxically, less developed and poorer areas had a lower prevalence, which may be a result of underreporting of birth weight information in these municipalities.

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.

Contextual risk factors for low birth weight: a multilevel analysis

BACKGROUND

Low birth weight (LBW) remains to be a leading cause of neonatal death and a major contributor to infant and under-five mortality. Its prevalence has not declined in the last decade in sub-Saharan Africa (SSA) and Asia. Some individual level factors have been identified as risk factors for LBW but knowledge is limited on contextual risk factors for LBW especially in SSA.

METHODS

Contextual risk factors for LBW in Ghana were identified by performing multivariable multilevel logistic regression analysis of 6,900 mothers dwelling in 412 communities that participated in the 2003 and 2008 Demographic and Health Surveys in Ghana.

RESULTS

Contextual-level factors were significantly associated with LBW: Being a rural dweller increased the likelihood of having a LBW infant by 43% (OR 1.43; 95% CI 1.01-2.01; P-value <0.05) while living in poverty-concentrated communities increased the risk of having a LBW infant twofold (OR 2.16; 95% CI 1.29-3.61; P-value <0.01). In neighbourhoods with a high coverage of safe water supply the odds of having a LBW infant reduced by 28% (OR 0.74; 95% CI 0.57-0.96; P-value <0.05).

CONCLUSION

This study showed contextual risk factors to have independent effects on the prevalence of LBW infants. Being a rural dweller, living in a community with a high concentration of poverty and a low coverage of safe water supply were found to increase the prevalence of LBW infants. Implementing appropriate community-based intervention programmes will likely reduce the occurrence of LBW infants.

Social inequalities in neonatal mortality and living condition

OBJECTIVE

To evaluate the association between the spatial distribution of neonatal mortality and living conditions, and to analyze trends in the social inequalities, related to this mortality, in Salvador, Bahia, Brazil, 2000 - 2006.

METHODS

The city's Information Zones, the unit of analysis used in this study, were grouped into strata reflecting high, intermediate, low and very low living conditions, based on a living conditions index (LCI). Neonatal mortality rates were calculated for each stratum. Spearman's correlation, linear regression and relative risks were used in the data analysis.

RESULTS

Neonatal mortality in Salvador was found to be associated with living conditions, with risks of 53, 56 and 59% greater, respectively, in the intermediate, low and very low strata, when compared to the high living conditions stratum. Only the intermediate living conditions stratum shows a significant decline in neonatal mortality (β = -0.93; p = 0.039). In the stratum of high living conditions, it was observed a stagnation of this mortality.

CONCLUSIONS

Poorer living conditions were associated to higher risks of neonatal mortality. The slight decline in social inequalities, found in neonatal mortality, was due to a decline in the intermediate living conditions stratum. Although dependent on the access to quality healthcare services and life support technologies, a more consistent reduction in the neonatal mortality and its associated inequalities will only be achieved when broader-reaching public policies are implemented, improving the living conditions, and mainly focusing on priority groups.

Low birth weight in São Luís, northeastern Brazil: trends and associated factors

BACKGROUND

To analyze trends in LBW (low birth weight) rate using birth registry data and identify factors associated with LBW in São Luís comparing two birth cohorts separated by a 12-year interval.

METHODS

2,426 births were included in 1997/98 and 5,040 in 2010. The dependent variable was LBW (<2,500 g). Multiple logistic regression was performed to determine the association of independent variables with LBW. Data were also obtained from SINASC (Brazilian National Birth Registry) to analyze stillbirth and LBW rates trends from 1996 to 2010, using 3-year moving averages.

RESULTS

LBW, intrauterine growth restriction (IUGR) and preterm birth rates did not differ between the two cohorts. Despite this, birth registry data showed increasing LBW rate up to 2001, coinciding with decreasing stillbirth rate. Both stillbirth and LBW rates decreased thereafter. A significant reduction was observed in the percentage of teenage mothers, mothers with up to 4 years of education, family income up to one minimum wage and mothers who did not attend prenatal care. There was an increase in maternal age ≥35 years and schooling ≥12 years. The variables associated with LBW in 1997/98 were young maternal age (<18 years), maternal smoking during pregnancy and primiparity. Variables that remained in the adjusted model in 2010 were female gender, income <3 minimum wages, lack of prenatal care, maternal smoking during pregnancy and primiparity.

CONCLUSIONS

Although LBW rate did not differ between the two cohorts, this apparent stability masked an increase up to 2001 and a decrease thereafter. The rise in LBW rate paralleled reduction in the stillbirth rate, suggesting improvement in obstetrical and newborn care. Maternal, socioeconomic and demographic factors associated with LBW differed between the two cohorts, except for smoking during pregnancy and parity that were significantly associated with LBW in both cohorts.

Risk factors for low birth weight in Rio Grande do Sul State, Brazil: classical and multilevel analysis

The objective of this study was to identify risk factors for low birth weight in singleton live born infants in Rio Grande do Sul State, Brazil, in 2003, based on data from the Information System on Live Births. The study used both classical multivariate and multilevel logistic regression. Risk factors were evaluated at two levels: individual (live births) and contextual (micro-regions). At the individual level the two models showed a significant association between low birth weight and prematurity, number of prenatal visits, congenital anomalies, place of delivery, parity, sex, maternal age, maternal occupation, marital status, schooling, and type of delivery. In the multilevel models, the greater the urbanization of the micro-region, the higher the risk of low birth weight, while in less urbanized micro-regions, single mothers had an increased risk of low birth considering all live births. Low birth weight varied according to micro-region and was associated with individual and contextual characteristics. Although most of the variation in low birth weight occurred at the individual level, the multilevel model identified an important risk factor in the contextual level.

Maternal education level and low birth weight: a meta-analysis

OBJECTIVE

To assess the association between maternal education level and birth weight, considering the circumstances in which the excess use of technology in healthcare, as well as the scarcity of these resources, may result in similar outcomes.

METHODS

A meta-analysis of cohort and cross-sectional studies was performed; the studies were selected by systematic review in the MEDLINE database using the following Key**words socioeconomic factors, infant, low birth weight, cohort studies, cross-sectional studies. The summary measures of effect were obtained by random effect model, and its results were obtained through forest plot graphs. The publication bias was assessed by Egger's test, and the Newcastle-Ottawa scale was used to assess study quality.

RESULTS

The initial search found 729 articles. Of these, 594 were excluded after reading the title and abstract; 21, after consensus meetings among the three reviewers; 102, after reading the full text; and three for not having the proper outcome. Of the nine final articles, 88.8% had quality ≥ six stars (Newcastle-Ottawa Scale), showing good quality studies. The heterogeneity of the articles was considered moderate. High maternal education showed a 33% protective effect against low birth weight, whereas medium degree of education showed no significant protection when compared to low maternal education.

CONCLUSIONS

The hypothesis of similarity between the extreme degrees of social distribution, translated by maternal education level in relation to the proportion of low birth weight, was not confirmed.

Birth in Brazil: national survey into labour and birth

BACKGROUND

Caesarean section rates in Brazil have been steadily increasing. In 2009, for the first time, the number of children born by this type of procedure was greater than the number of vaginal births. Caesarean section is associated with a series of adverse effects on the women and newborn, and recent evidence suggests that the increasing rates of prematurity and low birth weight in Brazil are associated to the increasing rates of Caesarean section and labour induction.

METHODS

Nationwide hospital-based cohort study of postnatal women and their offspring with follow-up at 45 to 60 days after birth. The sample was stratified by geographic macro-region, type of the municipality and by type of hospital governance. The number of postnatal women sampled was 23,940, distributed in 191 municipalities throughout Brazil. Two electronic questionnaires were applied to the postnatal women, one baseline face-to-face and one follow-up telephone interview. Two other questionnaires were filled with information on patients' medical records and to assess hospital facilities. The primary outcome was the percentage of Caesarean sections (total, elective and according to Robson's groups). Secondary outcomes were: post-partum pain; breastfeeding initiation; severe/near miss maternal morbidity; reasons for maternal mortality; prematurity; low birth weight; use of oxygen use after birth and mechanical ventilation; admission to neonatal ICU; stillbirths; neonatal mortality; readmission in hospital; use of surfactant; asphyxia; severe/near miss neonatal morbidity. The association between variables were investigated using bivariate, stratified and multivariate model analyses. Statistical tests were applied according to data distribution and homogeneity of variances of groups to be compared. All analyses were taken into consideration for the complex sample design.

DISCUSSION

This study, for the first time, depicts a national panorama of labour and birth outcomes in Brazil. Regardless of the socioeconomic level, demand for Caesarean section appears to be based on the belief that the quality of obstetric care is closely associated to the technology used in labour and birth. Within this context, it was justified to conduct a nationwide study to understand the reasons that lead pregnant women to submit to Caesarean sections and to verify any association between this type of birth and it's consequences on postnatal health.

Análise da distribuição espacial da mortalidade neonatal e de fatores associados, em Salvador, Bahia, Brasil, no período 2000-2006

Realizou-se estudo de agregados espaciais visando a identificar padrões na distribuição espacial da mortalidade neonatal, bem como fatores associados, em Salvador, Bahia, Brasil, 2000-2006. Foram construídos mapas temáticos e usadas técnicas para apreciação formal de dependência espacial. Mediante modelos de regressão linear múltipla (espacial e não espacial) verificou-se a relação entre distribuição espacial dessa mortalidade e fatores selecionados. Evidenciou-se autocorrelação espacial para a mortalidade neonatal (I = 0,17; p = 0,0100), não havendo, portanto, aleatoriedade em sua distribuição. Foi delineado um padrão espacial em que os maiores riscos (> 9,0/1.000 nascidos vivos) concentraram-se em áreas do centro e subúrbio, onde reside a população de menor condição socioeconômica, mostrando-se esta distribuição associada aos fatores de risco analisados. A proporção de nascidos vivos com baixo peso foi a única variável significativamente associada à mortalidade neonatal. Possivelmente, as condições de vida da população contribuíram para a desigual distribuição espacial da mortalidade neonatal nesse município.

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.

Determinants of preterm birth: Pelotas, Rio Grande do Sul State, Brazil, 2004 birth cohort

Prematurity is a leading cause of neonatal mortality and a global health problem that affects high, middle and low-income countries. Several factors may increase the risk of preterm birth. In this article, we test the hypothesis that different risk factors determine preterm birth in different income groups by investigating whether risk factors for preterm deliveries in the 2004 Pelotas (Rio Grande do Sul State, Brazil) birth cohort vary among those groups. A total of 4,142 women were included in the analysis. Preterm births were equally common among women who had spontaneous vaginal deliveries as for those with induced or operative births. In the multivariate analysis the factors that remained significantly associated with preterm birth were black skin color, low education, poverty, young maternal age, primiparity, previous preterm birth, inadequacy of prenatal care and reported hypertension. In the analyses repeated after stratification by family income terciles, there was no evidence of effect modification by income and no clear difference between the socioeconomic groups. No association between cesarean section and preterm delivery was found. Further studies are required to understand the causes of the epidemic of preterm births in Brazil.

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.

Baixo peso ao nascer no Brasil de acordo com as informações sobre nascidos vivos do Ministério da Saúde, 2005

Embora seja notório que a cobertura do Sistema de Informação sobre Nascidos Vivos (SINASC) esteja crescendo e que a qualidade da informação venha melhorando, desde a sua implantação, sabe-se que a enumeração de nascidos vivos ainda não é completa no Brasil. Neste trabalho, objetiva-se analisar as desigualdades da proporção do baixo peso ao nascer no Brasil, em 2005, segundo alguns aspectos como o geográfico, o tamanho da população do município e a escolaridade da mãe. Analisou-se, igualmente, a influência da atenção pré-natal. Considerando a totalidade dos nascidos vivos, evidenciou-se o paradoxo do baixo peso ao nascer, ou seja, foram encontrados percentuais mais elevados nas áreas de maior desenvolvimento sócio-econômico. Os resultados paradoxais são explicados, principalmente, pela menor sobrevida e registro inadequado dos prematuros nos municípios mais pobres. Levando-se em conta os nascidos vivos a termo de gestação não-múltipla, foram encontradas desigualdades por grau de escolaridade da mãe. Sugere-se que o atendimento pré-natal abrangente e com qualidade poderia ter um impacto maior na redução dos resultados adversos da gestação, contribuindo para a diminuição das desigualdades sócio-econômicas da saúde perinatal no Brasil.

Social inequality and perinatal health: comparison of three Brazilian cohorts

The objective of the present study was to estimate and compare social inequality in terms of three indicators, i.e., low birth weight (LBW), preterm birth (PTB) and small for gestational age (SGA) birth, in three birth cohorts. Two cohorts were from the city of Ribeirão Preto, where data were collected for all 6748 live born singletons in 1978/79 and for one third of live born singletons (2846) in 1994. The third cohort consisted of 2443 singletons born in São Luís over a period of one year (1997/98). In Ribeirão Preto, LBW and PTB rates increased in all social strata from 1978/79 to 1994. Social inequalities regarding LBW and PTB disappeared since the increase in these rates was more accelerated in the groups with higher educational level. The percentage of SGA infants increased over the study period. Social inequality regarding SGA birth increased due to a more intense increase in SGA births in the strata with lower schooling. In São Luís, in 1997/98 there was no social inequality in LBW or PTB rates, whereas SGA birth rate was higher in mothers with less schooling. We speculate that the more accelerated increase in medical intervention, especially due to the increase in cesarean sections in the more privileged groups, could be the main factor explaining the unexpected increase in LBW and PTB rates in Ribeirão Preto and the decrease or disappearance of social inequality regarding these perinatal indicators in the two cities.

Mortalidade neonatal precoce hospitalar em Minas Gerais: associação com variáveis assistenciais e a questão da subnotificação

INTRODUÇÃO: Os óbitos neonatais precoces estão relacionados com problemas de acesso à assistência de qualidade ao pré-natal, ao parto hospitalar e ao recém-nascido. Os hospitais em Minas Gerais estão distribuídos de forma heterogênea e isto pode se refletir em diferentes níveis de mortalidade neonatal (MN) entre as regiões do Estado. OBJETIVO: Investigar a MN precoce hospitalar no Sistema de Informações Hospitalares (SIH/SUS) e avaliar possível associação da taxa de mortalidade neonatal precoce obtida a partir do SIH/SUS (TMNP_SIH), com variáveis relativas ao atendimento à gestante e ao recém-nascido em estratos de municípios homogêneos. MÉTODO: Utilizou-se o SIH/SUS para obter o número de nascimentos e óbitos segundo o município de residência. Os municípios foram agrupados segundo microrregião e tamanho populacional, totalizando 199 grupamentos. O método CART (Classification and Regression Tree) identificou três estratos de grupamentos de municípios homogêneos do ponto de vista socioeconômico. Para cada estrato utilizou-se a matriz de correlação de Spearman para avaliar associação entre a TMNP e indicadores da assistência. RESULTADOS: A TMNP_SIH para Minas Gerais foi de 10,9/1000 nascidos vivos. Observou-se maior probabilidade de TMNP_SIH menor que 8/1000 nascidos vivos onde a situação socioeconômica é mais precária. Observou-se correlação positiva entre TMNP_SIH e berços por mulher em idade fértil e baixo peso ao nascer no Estrato 1, e entre TMNP_SIH e médicos por habitante no Estrato 3. CONCLUSÃO: Questões relativas ao acesso à assistência, sub-registro de óbitos e erro de classificação de neomorto como natimorto podem estar se refletindo na TMNP_SIH. O volume de nascimentos e óbitos registrados no SIH/SUS justifica investimentos na qualidade desses registros e sua utilização em estudos epidemiológicos.

The epidemiology of preterm labour--why have advances not equated to reduced incidence?

The major burden of preterm birth is in the developing world, where most of the increasing death and morbidity is secondary to infectious diseases such as malaria, HIV, tuberculosis, bacterial vaginosis and intestinal parasites. In some developing countries, the growth of medical care has outstripped the growth of preventive public health, with an associated increase in iatrogenic preterm births. In developed countries, more than one-third of preterm births are medically indicated because of conditions such as fulminating pre-eclampsia or severe intrauterine growth restriction. Neither of these conditions is currently preventable. One in five preterm births is associated with multiple pregnancy, and these have been greatly increased by assisted reproduction techniques. The use of tocolytics has proved disappointing perhaps because inflammation rather than spontaneous uterine activity is increasingly recognised as the final common pathway. Inappropriate antibiotics used late in pregnancy are ineffective and may have adverse effects. Currently, the most promising interventions are public health related and include reducing the transmission of communicable diseases, improvements in the management of diabetes and reduction in harmful behaviours such as smoking and drug abuse.

Is low birthweight associated with dental caries in permanent dentition?

The aim of this study was to test the hypothesis of association between low birthweight and dental caries. This study used data from the Third National Health and Nutritional Examination Survey, 1988-94 (NHANES III) including 7- to 11-year-old children with complete dental caries information (n = 2439). Two case definitions for dental caries were used: presence of the disease in more than one tooth, and more than 10% of teeth with dental caries. Low birthweight was defined as those children born weighing <2500 g. Other covariates used in the analysis were sex, age, poverty level, race/ethnicity, frequency of dental visit, education of head of household, daily sucrose intake, blood lead level and blood cotinine level. A separate analysis was conducted for each case definition of dental caries. Bivariable and stratified analysis was performed followed by multivariable Poisson regression. The Stata 8.0 statistical package was used to take into consideration the multistage complex sample. For the definition of more than one tooth with dental caries, the prevalence ratios (PRs) for bivariable and multivariable analyses were 1.28 [95% confidence interval (CI): 0.48, 3.42] and 1.01 [95% CI: 0.41, 2.49] respectively. For the definition of >10% of teeth with dental caries, the PRs for bivariable and multivariable analyses were 1.33 [95% CI: 0.60, 2.96] and 1.32 [95% CI: 0.75, 2.30] respectively. This study could not demonstrate an association between low birthweight and dental caries in permanent teeth of 7- to 11-year-old American children.

Which factors could explain the low birth weight paradox?

OBJECTIVE: Low birth weight children are unusual among well-off families. However, in Brazil, low birth weight rate was higher in a more developed city than in a less developed one. The study objective was to find out the reasons to explain this paradox. METHODS: A study was carried out in two municipalities, Ribeirão Preto (Southeastern Brazil) and São Luís (Northeastern Brazil), which low birth weight rates were 10.7% and 7.6% respectively. Data from two birth cohorts were analyzed: 2,839 newborns in Ribeirão Preto in 1994 and 2,439 births in São Luís in 1997-1998. Multiple logistic regression analysis was performed, adjusted for confounders. RESULTS: Low birth weight risk factors in São Luís were primiparity, maternal smoking and maternal age less than 18 years. In Ribeirão Preto, the associated variables were family income between one and three minimum wages, maternal age less than 18 and equal to or more than 35 years, maternal smoking and cesarean section. In a combined model including both cohorts, Ribeirão Preto presented a 45% higher risk of low birth weight than São Luís. When adjusted for maternal smoking habit, the excess risk for low birth weight in Ribeirão Preto compared to São Luís was reduced by 49%, but the confidence interval was marginally significant. Differences in cesarean section rates between both cities contributed to partially explain the paradox. CONCLUSIONS: Maternal smoking was the most important risk factor for explaining the difference in low birth weight between both cities. The other factors contributed little to explain the difference in low birth weight rates.

Sistemas de informação e mortalidade perinatal: conceitos e condições de uso em estudos epidemiológicos

O monitoramento da mortalidade perinatal depende da qualidade dos dados dos sistemas de informação. As diferentes definições para a notificação e cálculo da mortalidade perinatal podem afetar a magnitude e análise dos seus componentes. Comparou-se a disponibilidade de informações sobre nascidos vivos, óbitos fetais e neonatais precoces no Registro Civil, SIM e SINASC para oito unidades da federação com cobertura de eventos acima de 90%, em 2002. Verificou-se que o SINASC apresenta maior cobertura de eventos que o registro civil e excelente completude de dados (superior a 99%). O SIM apresenta situação distinta, há elevada ausência de informação sobre peso ao nascer (23,4%), idade gestacional (9,1%), idade da mãe (18,5%), tipo de gravidez (13,8%) e anos de estudo da mãe (40,6%), para os óbitos fetais. Os óbitos neonatais precoces apresentam comportamento semelhante, com ausência do registro do peso ao nascer em 22,6%, idade gestacional (17,8%), tipo de gravidez (19,1%), idade (27,9%) e escolaridade da mãe (38,5%). Não foi possível caracterizar se os óbitos fetais eram intra-parto ou ante-parto por falta de informação. No entanto, estes dados poderiam ser facilmente obtidos, pois mais de 95% dos eventos ocorreram em estabelecimentos hospitalares. Os critérios para notificação de óbitos fetais e nascidos vivos nos sistemas de informação dificultam a comparação internacional da magnitude e da participação de seus componentes da mortalidade perinatal. A ausência de informações compromete a obtenção de indicadores específicos, dificultando as atividades de monitoramento. Algumas atividades são indicadas para o aprimoramento do SIM.

The epidemiology of preterm labor--a global perspective

The major burden of preterm birth is in the developing world, where much of the death and morbidity is secondary to infectious diseases such as malaria, HIV, tuberculosis and intestinal parasites. There is some evidence to support the concept that normal gestational length varies with ethnic group; babies of black African ancestry tend to be born earlier, more commonly pass meconium in labor, but have less respiratory distress than white European babies of matched gestational age. However, ethnic differences are tiny compared with the effects of infectious disease and malnutrition. Interventions to prevent preterm birth should predominantly be aimed at the prevention and treatment of infectious disease, and the improvement of maternal nutrition. Without this, medical intervention tends to increase the rate of preterm birth without corresponding improvement in outcomes.