Determinantes do baixo peso ao nascer a partir das Declarações de Nascidos Vivos

Spatial patterns of mortality in low birth weight infants at term and its determinants in the State of São Paulo, Brazil

OBJECTIVE

Low birth weight (LBW) is a public health problem strongly associated with infant mortality. This study aimed to identify the spatial distribution of infant mortality in newborns with LBW (750-2,500 g) at term (≥37 weeks of gestation), due to their being small for gestational age, analyzing its association with mother-related determinants, as well as to identify priority areas of mortality in the State of São Paulo, 2010-2019.

METHODS

Infant mortality rate was analyzed in the division of neonatal mortality and postneonatal mortality of newborns with LBW at term. The empirical Bayesian method smoothed the rates, the univariate Moran index was used to measure the degree of spatial association between the municipalities, and the bivariate Moran index was employed to identify the existence of a spatial association between the rates and the selected determinants. Thematic maps of excess risk and local Moran were prepared to identify spatial clusters, adopting 5% as a significance level.

RESULTS

The excess risk map showed that more than 30% of the municipalities had rates above the state rate. High-risk clusters were identified in the southwest, southeast, and east regions, mainly among more developed municipalities. The determinants of adolescent mothers, mothers over 34 years of age, low education, human development index, social vulnerability index, gross domestic product, physicians, and pediatric beds showed a significant association with the rates evaluated.

CONCLUSIONS

Priority areas and significant determinants associated with reduced mortality in newborns with LBW were identified, suggesting the need for intervention measures to achieve the Sustainable Development Goal.

Need for oxygen therapy and ventilatory support in premature infants in a hospital in Southern Brazil

BACKGROUND

Prematurity in newborns is a condition that is associated with worse hospital outcomes when compared to birth to term. A preterm infant (PI) is classified when gestational age (GA) < 37 wk.

AIM

To analyze prognostic indicators related to the use of oxygen therapy, non-invasive ventilation (continuous positive airway pressure) and mechanical ventilation (MV) in PI.

METHODS

This is a retrospective cohort. The sample was composed of PIs from a private hospital in southern Brazil. We included neonates with GA < 37 wk of gestation in the period of January 1, 2018 to December 31, 2018. For data collection, electronic records were used in the Tasy Philips^TM system, identifying the variables: maternal age, type of birth, prenatal information, GA, Apgar score, birth weight, neonatal morbidities, vital signs in the 1st hour at birth, need for oxygen therapy, continuous positive airway pressure and MV, hospitalization in the neonatal intensive care unit, length of stay and discharge or death.

RESULTS

In total, 90 PI records were analyzed. The median (p25-p75) of GA was 34.0 (31.9-35.4) wk, and there were 45 (50%) males. The most common morbidity among PIs was the acute respiratory discomfort syndrome, requiring hospitalization in the neonatal intensive care unit in 76 (84.4%) cases. The utilization rate of oxygen therapy, continuous positive airway pressure and MV was 12 (13.3%), 37 (41.1%) and 13 (14.4%), respectively. The median (p25-p75) length of stay was 12.0 (5.0-22.2) d, with 10 (11.1%) deaths. A statistical association was observed with the use of MV and GA < 28 wk, lower maternal age, low birth weight, Apgar < 8 and neonatal deaths.

CONCLUSION

The identification of factors related to the need for MV in prematurity may help in the indication of a qualified team and technologies to promptly meet the unforeseen events that may occur after birth.

The intergenerational relationship between conditional cash transfers and newborn health

Background

Lack of nutrition, inadequate housing, low education and limited access to quality care can negatively affect children’s health over their lifetime. Implemented in 2003, the Bolsa Familia (“Family Stipend”) Program (PBF) is a conditional cash transfer program targeting poor households in Brazil. This study investigates the long-term benefits of cash transfers through intergenerational transmission of health and poverty by assessing the early life exposure of the mother to the PBF.

Methods

We used data from the 100M SINASC-SIM cohort compiled and managed by the Center for Data and Knowledge Integration for Health (CIDACS), containing information about participation in the PBF and socioeconomic and health indicators. We analyzed five measures of newborn health: low (less than 2,500 g) and very low (less than 1,500 g) birth weight, premature (less than 37 weeks of gestation) and very premature (less than 28 weeks of gestation) birth, and the presence of some type of malformation (according to ICD-10 codes). Furthermore, we measured the early life exposure to the PBF of the mother as PBF coverage in the previous decade in the city where the mother was born. We applied multilevel logistic regression models to assess the associations between birth outcomes and PBF exposures.

Results

Results showed that children born in a household where the mother received BF were less likely to have low birth weight (OR 0.93, CI; 0.92-0.94), very low birth weight (0.87, CI; 0.84-0.89), as well as to be born after 37 weeks of gestation (OR 0.98, CI; 0.97-0.99) or 28 weeks of gestation (OR 0.93, CI; 0.88-0.97). There were no significant associations between households where the mother received BF and congenital malformation.

On average, the higher the early life exposure to the PBF of the mother, the lower was the prevalence of low birth weight, very low birth weight and congenital malformation of the newborn. No trend was noted for preterm birth.

Conclusion

The PBF might have indirect intergenerational effects on children’s health. These results provide important implications for policymakers who have to decide how to effectively allocate resources to improve child health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-12565-7.

Associations between Maternal Dietary Patterns and Infant Birth Weight in the NISAMI Cohort: A Structural Equation Modeling Analysis

The mother’s diet during pregnancy is associated with maternal and child health. However, there are few studies with moderation analysis on maternal dietary patterns and infant birth weight. We aim to analyse the association between dietary patterns during pregnancy and birth weight. A prospective cohort study was performed with pregnant women registered with the prenatal service (Bahia, Brazil). A food frequency questionnaire was used to evaluate dietary intake. Birth weight was measured by a prenatal service team. Statistical analyses were performed using factor analysis with a principal component extraction technique and structural equation modelling. The mean age of the pregnant women was 27 years old (SD: 5.5) and the mean birth weight was 3341.18 g. It was observed that alcohol consumption (p = 0.05) and weight-gain during pregnancy (p = 0.05) were associated with birth weight. Four patterns of dietary consumption were identified for each trimester of the pregnancy evaluated. Adherence to the “Meat, Eggs, Fried Snacks and Processed foods” dietary pattern (pattern 1) and the “Sugars and Sweets” dietary pattern (pattern 4) in the third trimester directly reduced birth weight, by 98.42 g (Confidence interval (CI) 95%: 24.26, 172.59) and 92.03 g (CI 95%: 39.88, 165.30), respectively. It was also observed that insufficient dietary consumption in the third trimester increases maternal complications during pregnancy, indirectly reducing birth weight by 145 g (CI 95%: −21.39, −211.45). Inadequate dietary intake in the third trimester appears to have negative results on birth weight, directly and indirectly, but more studies are needed to clarify these causal paths, especially investigations of the influence of the maternal dietary pattern on the infant gut microbiota and the impacts on perinatal outcomes.

Geographical variations in maternal dietary patterns during pregnancy associated with birth weight in Shaanxi province, Northwestern China

The geographical variation of maternal dietary patterns related to birth outcomes is important for improving the health of mothers and children; however, it is currently unknown. Thus, the objective of the study was to investigate geographical variations of maternal dietary pattern during pregnancy, and evaluate the spatial varying association of maternal dietary patterns in pregnancy with abnormal birth weight. A population-based cross-sectional study was conducted in Shaanxi province in Northwest China in 2013 to evaluate the relationship between abnormal birth weight and dietary pattern using the Geographically Weighted Logistic Regression (GWLR). Three dietary patterns during pregnancy were extracted through factor analysis, explaining approximately 45.8% of the variability of food intake. Approximately 81.6% of mothers with higher scores on the equilibrium pattern was more unlikely to have small for gestational age (SGA) infants, with the lower OR observed in Central and South Shaanxi. The snacks pattern was positively associated with low birth weight (LBW) for 23.2% of participants, with the highest OR in Central Shaanxi. Among about 80.0% of participants with higher scores on the snacks pattern living in South and Central Shaanxi, there was a higher risk for SGA. The OR values tend to descend from South to North Shaanxi. The OR values of the negative association between prudent pattern and LBW decreased from South to North Shaanxi among approximately 59.3% of participants. The prudent pattern was also negatively associated with the increasing risk of fetal macrosomia among 19.2% of participants living mainly in South Shaanxi. The association of maternal dietary patterns during pregnancy with abnormal birth weight varied geographically across Shaanxi province. The findings emphasize the importance of geographical distribution to improve the dietary patterns among disadvantaged pregnant women.

Low birth weight and its associated factors

OBJECTIVE

To calculate the frequency and evaluate the factors associated with low birth weight.

METHODS

A retrospective study, with data from pregnant women who participated in the Programa de Atenção às Gestantes do Programa Einstein na Comunidade de Paraisópolis, between 2011 and 2014, and who returned for the postpartum evaluation of their newborns. Variables related to the pregnant woman, pregnancy, and newborn were evaluated. The outcome variable was low birth weight, defined as <2.5kg. The associations between the independent variables and low birth weight were assessed by χ2 and Mann-Whitney tests. Logistic regression models analyzed the combined effects of the independent variables on low birth weight.

RESULTS

Data of 794 pregnant women and their newborns (52.1% males) were analyzed. The age of pregnant women varied from 13 to 44 years (median of 24 years), and the majority reported being married or living in cohabitation (74.7%), and having between 9 to 11 years of schooling (53.4%). The proportion of low birth weight was 7.6% (newborn mean weight of 3.2kg) and, in multivariate analysis, presence of twinning, age group of the pregnant women (showing protection for low birth weight between ages ≥18 years and <35 years), and cesarean section were associated with low birth weight.

CONCLUSION

The proportion of low birth weight was 7.6% and twining, age of the pregnant woman, and cesarean delivery were associated with the occurrence of low birth weight.

Regional differences and factors associated with the number of prenatal visits in Brazil: analysis of the Information System on Live Births in 2013

Objective:

To investigate factors associated with seven or more prenatal visits, in Brazil, in 2013.

Methods:

Cross-sectional study from the database of Information System on Live Births. The association of explanatory variables was tested with prenatal visits by means of the analysis of single and multiple multinomial regressions. The spatial distribution of prenatal visits according to the Brazilian municipalities was also analyzed.

Results:

It was found that 2.7% of pregnant women attended no prenatal visit and 63.1% attended 7 or more. The chance to attend 7 or more prenatal visits was higher among pregnant women aged 40 years or more, with 12 years or more of schooling, living with a roommate, living in the South and Southeast regions, who had a triplet or more pregnancy, with gestational age of 42 weeks or more, and who had children with normal birth weight. Significant regional disparities were identified in the prevalence of women with seven or more prenatal visits.

Conclusion:

Although Brazil has a Unified Health System that provides universal prenatal care, the use of this service is uneven according to geographic, demographic, and socioeconomic characteristics.

[Prenatal care and risk factors associated with premature birth and low birth weight in the a capital in the Brazilian Northeast]

The main determinants of the risk of mortality in the neonatal period are low birth weight and premature birth. The study sought to analyze the adequacy of prenatal care and risk factors associated with premature birth and low birth weight in a northeastern Brazilian capital. This is a case-control study. A model for adequacy of prenatal conditions composed of four indicators was created. Descriptive statistics for univariate analysis were used; as well as Wald linear trend tests, Student's t and chi-square test for bivariate analysis and multiple logistic regression for multivariate analysis with p <0.05. Multivariate analysis showed that poor education, not performing gainful activity, caesarean section, oligohydramnios, placental abruption and pre-eclampsia are independent factors associated with premature birth and/or low birth weight. For adequacy of prenatal care, variable indicator III remained significant, showing that mothers who had inadequate prenatal care had an increased chance for the occurrence of the outcome, highlighting the need for adequate public health policies of care for pregnant women in the municipality under scrutiny.

Dietary patterns in pregnancy and birth weight

OBJECTIVE

To analyze if dietary patterns during the third gestational trimester are associated with birth weight.

METHODS

Longitudinal study conducted in the cities of Petropolis and Queimados, Rio de Janeiro (RJ), Southeastern Brazil, between 2007 and 2008. We analyzed data from the first and second follow-up wave of a prospective cohort. Food consumption of 1,298 pregnant women was assessed using a semi-quantitative questionnaire about food frequency. Dietary patterns were obtained by exploratory factor analysis, using the Varimax rotation method. We also applied the multivariate linear regression model to estimate the association between food consumption patterns and birth weight.

RESULTS

Four patterns of consumption – which explain 36.4% of the variability – were identified and divided as follows: (1) prudent pattern (milk, yogurt, cheese, fruit and fresh-fruit juice, cracker, and chicken/beef/fish/liver), which explained 14.9% of the consumption; (2) traditional pattern, consisting of beans, rice, vegetables, breads, butter/margarine and sugar, which explained 8.8% of the variation in consumption; (3) Western pattern (potato/cassava/yams, macaroni, flour/farofa/grits, pizza/hamburger/deep fried pastries, soft drinks/cool drinks and pork/sausages/egg), which accounts for 6.9% of the variance; and (4) snack pattern (sandwich cookie, salty snacks, chocolate, and chocolate drink mix), which explains 5.7% of the consumption variability. The snack dietary pattern was positively associated with birth weight (β = 56.64; p = 0.04) in pregnant adolescents.

CONCLUSIONS

For pregnant adolescents, the greater the adherence to snack pattern during pregnancy, the greater the baby’s birth weight.

Frequência e características maternas e do recém nascido associadas à internação de neonatos em UTI no município de Joinville, Santa Catarina - 2012

Resumo Objetivos: determinar a frequência e os fatores associados à internação de recém-nascidos em UTI neonatal no município de Joinville, Santa Catarina. Métodos: estudo transversal com base nos registros de nascidos vivos (DNV) e de internações em Unidades de Terapia Intensivas (UTI) neonatais em 2012. Para avaliar associações entre variáveis explicativas e desfecho foram estimados odds ratios (OR) brutos e ajustados e respectivos intervalos de confiança de 95% com a técnica de regressão logística. Resultados: a frequência de internação em UTI neonatal foi de 11,7% (9,69-13,7). Baixo peso ao nascer (ORaj = 8,1 [6,3 - 10,3]), malformação congênita (ORaj = 6,0 [3,2 – 11,2]), Apgar de 5º minuto < 7 (ORaj = 5,7 [2,6 - 12,3]), prematuridade (ORaj = 3,4 [(2,7 – 4,1]), sexo masculino (ORaj = 1,5 [1,2 - 1,8]), hospital público (ORaj = 2,0 [1,6 - 2,4]), mãe sem companheiro (ORaj = 1,4 [1,2 - 1,7]), baixa escolaridade materna (ORaj = 1,4 [1,2 - 1,7]) e < 7 consultas no pré natal (ORaj = 1,3[1,1 - 1,6]) constituíram fatores de risco para internação. Conclusões: as características biológicas dos recém-nascidos associadas à internação em UTI neonatal são passíveis de prevenção, evidenciando a importância da qualificação da assistência à gestante e recém-nascido.

Baixo peso ao nascer em adolescentes e adultas jovens na Região Nordeste do Brasil

Objetivos: avaliar a associação entre as características sociodemográficas, do pré-natal e do parto de mães adolescentes e adultas jovens com o baixo peso ao nascer, em capitais e outros municípios da Região Nordeste do Brasil, no período de 2011 e 2012. Métodos: estudo transversal, de base hospitalar e nível regional, realizado em 2011 e 2012. As informações foram obtidas por meio de entrevista com a puérpera no pós-parto imediato e coletados dados dos prontuários maternos e dos recém-nascidos. Um modelo teórico conceitual foi estabelecido com três níveis de hierarquia e a variável dependente foi o baixo peso ao nascer (BPN). Resultados: do total de 3009 puérperas entrevistadas, 9,7% apresentaram conceptos com baixo peso. As puérperas que realizaram menos que seis consultas no pré-natal apresentaram uma chance 1,7 vezes maior de ter RN com baixo peso; ser primigesta aumentou a chance da ocorrência do BPN em 1,5 vezes; assim como a prematuridade que representou o principal fator de exposição, elevando em 21 vezes a chance desse desfecho. Conclusões: o estudo demonstrou alta frequência de baixo peso ao nascer entre mães adolescentes e adultas jovens, tendo como principais fatores associados o número insuficiente de consultas pré-natal, primigestação e prematuridade.

[Birth weight in Brazilian children under two years of age]

Low birth weight is associated with increased risk of dying in the first year of life. This study was motivated by recent changes in the determination of birth weight patterns with the advent of the perinatal epidemiological transition. We analyzed data from the Brazilian National Survey of Demographic and Health of Children and Women including only children < 24 months. Prevalence of low birth weight in Brazil was 6.1%. Risk factors included female gender, residence in the South and Southeast geographic regions, low maternal education, and maternal smoking. The low birth weight profile changed, with higher prevalence in more economically developed regions, reflecting the neonatal epidemiological transition determined by changes in patterns of childbirth care and incorporation of perinatal life support technologies, in addition to the previously known biological risks associated with poverty and misinformation.

Filho J, Silva CFD. Gravidez na adolescência e baixo peso ao nascer: existe associação?

OBJETIVO: Verificar a associação entre gravidez na adolescência (dez a 19 anos) e baixo peso ao nascer. MÉTODOS: Estudo transversal realizado em maternidade terciária entre junho de 2000 a junho de 2001. Por sorteio aleatório simples, foram selecionadas mães adolescentes e não adolescentes entrevistadas no primeiro dia após o parto. Aplicou-se a análise multivariada por meio de regressão logística das variáveis implicadas com o baixo peso ao nascer. RESULTADOS: Foram selecionadas 539 duplas (mães e seus respectivos recém-nascidos), sendo 331 (61,4%) mulheres com 20 anos ou mais e 208 (38,5%) abaixo de 20 anos. Entre as adolescentes, 50 bebês (24%) tiveram idade gestacional <37 semanas, enquanto entre as mães acima de 20 anos, 52 (15,7%) eram prematuros (OR 1,58; IC95% 1,00-2,51). Entre as adolescentes, ocorreram 52 (25%) recém-nascidos com peso <2500g e, entre as adultas, 56 (16,9%) tinham baixo peso (OR 1,64; IC95% 1,05-2,56). Entre as que realizaram pré-natal adequado, a ocorrência de baixo peso foi de 12,3% e de 22,1% no grupo cuja assistência foi inadequada. Nesta casuística, a associação encontrada na análise univariada entre baixo peso e mãe adolescente não se manteve na análise multivariada. CONCLUSÕES: Baixo peso ao nascer em gestações na adolescência não pode ser atribuído isoladamente à idade materna.

Associação entre abuso de álcool durante a gestação e o peso ao nascer

OBJETIVO: Analisar a associação entre abuso de álcool durante a gestação e baixo peso ao nascer. MÉTODOS: Estudo transversal de base populacional aninhado a uma coorte de 957 gestantes que realizaram acompanhamento pré-natal no Sistema Único de Saúde da cidade de Pelotas, RS, e deram à luz entre setembro de 2007 e setembro de 2008. As mães foram entrevistadas em dois momentos distintos: no período de pré-parto e após o parto. Para verificar o abuso do álcool foi utilizada a escala Cut down, Annoyed by criticism, Guilty and Eye-opener. Foram realizadas análises bivariadas e regressão logística múltipla, ajustada pelas variáveis prematuridade e abuso de álcool. O nível de significância adotado foi de 95%. RESULTADOS: Das mulheres que participaram do estudo, 2,1% abusaram de álcool na gestação e, entre essas, 26,3% tiveram filhos com baixo peso. Houve associação entre o abuso de álcool e baixo peso ao nascer (p < 0,038). CONCLUSÕES: Os achados indicam que o abuso de álcool durante a gestação está associado ao baixo peso ao nascer.

Poluição ambiental, residência materna e baixo peso ao nascer

Estudo caso-controle, que objetivou analisar os fatores de risco associados ao baixo peso ao nascer de recém-nascidos de mães de Rio Grande-RS residentes nas proximidades da área industrial. Foram entrevistadas mães que deram à luz nas maternidades do município, durante os meses de abril a novembro de 2003. A amostra compreendeu 138 casos e 409 controles. Foi realizada análise estatística bivariada e multivariada. O Baixo Peso ao Nascer (BPN) manteve-se associado positivamente com natimortos prévios, BPN prévios, presença de hipertensão arterial durante a gestação e ameaça de aborto durante a gravidez atual. Foi possível identificar os principais fatores de risco a que estão expostas as gestantes e que interferem no peso ao nascer de seus filhos, os quais vêm somar-se àqueles decorrentes de uma maior exposição a poluentes, por residirem próximo às indústrias.

Resultados perinatais nos extremos da vida reprodutiva e fatores associados ao baixo peso ao nascer

Objetivou-se investigar os resultados perinatais nos extremos da vida reprodutiva e verificar os fatores de risco para o baixo peso ao nascer. Trata-se de um estudo retrospectivo dos partos ocorridos no município de Sarandi, Paraná, no ano de 2008, a partir de consultas aos dados do Sistema de Informação de Nascidos Vivos. As 331 gestantes foram subdivididas em dois grupos: adolescentes (10-19 anos) e tardias (35 anos ou mais). As taxas de parto cesáreo foram significativamente maiores (66,1%) nas gestantes com 35 anos ou mais do que nas adolescentes (26,8%). Quanto aos fatores de risco para o baixo peso ao nascer, observou-se que este esteve fortemente associado com prematuridade e o estado civil. Os resultados perinatais das gestantes com 35 anos ou mais não apresentaram diferença significativa quando comparados aos resultados das adolescentes, confirmando a ocorrência de resultados adversos nos dois extremos da vida reprodutiva, exceto pela ocorrência de parto cesáreo.

Spatial distribution and self-correlation of mother and child health indicators in the state of Parana, Brazil

Aiming to analyze the spatial distribution and self-correlation of data of mother-child health in Parana, Brazil, variables were selected from the Information System on Live Births, grouped into socioeconomic indicators: teenage mother, low education, high parity, race/color black of newborn; healthcare indicators: the prenatal coverage, prematurity and cesarean delivery and result indicators: low birth weight. The indicators were distributed in thematic maps and spatial self-correlation was measured using Moran's index that quantifies the degree of self-correlation. There was significant spatial self-correlation of teenage mother, low education and high parity of the "high-high" type in the macro-regions East, Campos Gerais and South; of low coverage of antenatal care in Campos Gerais, Central-south and North and of cesarean delivery in the Northwest. Elevated proportions of indicators of risk to the health of mother and child were found in the regions East, Campos Gerais and South. These results support the evaluation and planning of health services.

Parto prematuro de adolescentes: influência de fatores sociodemográficos e reprodutivos, Espírito Santo, 2007

A gravidez na adolescência é um problema de saúde pública, podendo trazer consequências negativas para a adolescente, sua família e para o concepto/recém-nascido. Objetivos: Identificar diferenças entre as características sociodemográficas e reprodutivas das mães adolescentes com parto a termo e com parto pré-termo, no Espírito Santo em 2007. Metodologia: Estudo retrospectivo quantitativo. Os dados foram coletados no Sistema de Informação de Nascidos Vivos, sendo realizada análise descritiva de 9.841 Declarações de Nascidos Vivos. A relação entre a variável dependente (termo) e fatores foi testada pelo teste exato de Fisher, com á=0,05. Os resultados evidenciaram que as diferenças nas características das mães adolescentes com parto a termo e pré-termo ocorreram nas seguintes variáveis: idade entre 10 a 14 anos (p=0,016), estado civil casada (p=0,014), número de consultas pré-natais quando insuficientes (p=0,000) e gestação dupla (p=0,000). Houve maior incidência de partos prematuros no Sistema Único de Saúde (p=0,000).

Diferenciais intra-urbanos de peso ao nascer no município de São Paulo

OBJETIVO: Identificar diferenciais intra-urbanos e fatores de risco na prevalência de baixo peso ao nascer. MÉTODOS: Foram utilizadas as informações das declarações de nascido vivo de mães residentes no município de São Paulo, obtidos do Sistema de Informação de Nascidos Vivos e Fundação Seade, para o período de 2002 e 2003, totalizando 368.980 nascidos vivos. Os endereços foram geo-referenciados em setores censitários e classificados em seis grupos de vulnerabilidade segundo o Índice Paulista de Vulnerabilidade Social. Para identificação dos possíveis fatores de risco empregou-se análise de regressão logística. RESULTADOS: Observou-se tendência de crescimento da prevalência de baixo peso ao nascer com aumento da vulnerabilidade (de 6,8% a 8,1%). Houve diferenças significativas entre os grupos quanto às características maternas, assistência pré-natal e da proporção de nascimentos de não pré-termo de baixo peso. No grupo de baixo peso não pré-termo, proxy da presença de retardo do crescimento intra-uterino, residir em áreas vulneráveis (1,29;1,17-1,43) e características socioeconômicas maternas desaforáveis, como mães adolescentes (1,13;1,04-1,22), baixa escolaridade (1,26;1,17-1,35) e elevada paridade (1,10;1,01-1,20) foram fatores de risco, assim como mães idosas (1,38;1,30-1,47), e sem companheiro (1,15;1,11-1,20). A ausência de pré-natal apresentou o maior risco de baixo peso para nascimentos de pré-termo (3,39;2,86-4,02) e não pré-termo (2,12;1,87-2,41). Houve redução de risco de baixo peso com o aumento de consultas de pré-natal para nascimentos de pré-termo e não pré-termo. CONCLUSÕES: Há diferenças de prevalência de baixo peso ao nascer segundo grupos de vulnerabilidade. A assistência pré-natal mostrou-se desigual segundo grupos de vulnerabilidade e seu elevado risco para o baixo peso ao nascer indica a importância de ampliar o acesso e qualidade dos serviços de saúde.