Abstracts

Introduction

Birth weight is an important predictor of perinatal, infant, and preschool-age children morbimortality, associated with diverse health outcomes in childhood and adulthood ¹1. Wilcox AJ. On the importance - and the unimportance - of birthweight. Int J Epidemiol 2001; 30:1233-41.^,22. Blencowe H, Cousens S, Chou D, Oestergaard M, Say L, Moller A-B, et al. Born too soon: the global epidemiology of 15 million preterm births. Reprod Health 2013; 10 Suppl 1:S2.. Recent Brazilian studies based on data from the Brazilian Information System on Live Births (SINASC) and local birth cohorts stressed the role of socioeconomic factors, access to prenatal care, increased rates of cesarian sections, and early-term births in determining low birth weitht ³3. Andrade CLT, Szwarcwald CL, Castilho EA. Baixo peso ao nascer no Brasil de acordo com as informações sobre nascidos vivos do Ministério da Saúde, 2005. Cad Saúde Pública 2008; 24:2564-72.^,44. Silveira MF, Victora CG, Horta BL, Silva BGC, Matijasevich A, Barros FC. Low birthweight and preterm birth: trends and inequalities in four population-based birth cohorts in Pelotas, Brazil, 1982-2015. Int J Epidemiol 2019; 48 Suppl 1:i46-53..

Recent studies reported pronounced health disparities separating Brazilian non-indigenous from indigenous children, who experience elevated rates of mortality, chronic undernutrition, preventable infectious diseases, and inadequate prenatal care ⁵5. Coimbra Jr. CEA, Santos RV, Welch JR, Cardoso AM, Souza MC, Garnelo L, et al. The First National Survey of Indigenous People's Health and Nutrition in Brazil: rationale, methodology, and overview of results. BMC Public Health 2013; 13:52.^,66. Santos RV, Borges GM, Campos MB, Queiroz BL, Coimbra Jr. CEA, Welch JR. Indigenous children and adolescent mortality inequity in Brazil: What can we learn from the 2010 National Demographic Census? SSM Popul Health 2020; 10:100537.^,77. Garnelo L, Horta BL, Escobar AL, Santos RV, Cardoso AM, Welch JR, et al. Avaliação da atenção pré-natal ofertada às mulheres indígenas no Brasil: achados do Primeiro Inquérito Nacional de Saúde e Nutrição dos Povos Indígenas. Cad Saúde Pública 2019; 35 Suppl 3:e00181318.. Information about indigenous children’s birth weight is scarce and often restricted to a limited number of people within specific ethnic groups ⁸8. Barreto CTG. Prevalência de baixo peso ao nascer e fatores associados em crianças indígenas Guarani no Sul e Sudeste: uma análise na linha de base da primeira coorte de nascimentos indígenas no Brasil [Tese de Doutorado]. Rio de Janeiro: Escola Nacional de Saúde Pública Sergio Arouca, Fundação Oswaldo Cruz; 2018.^,99. Bresan D, Pontes ERJC, Leite MS. Fatores associados ao peso ao nascer de crianças indígenas Terena, residentes na área urbana de Campo Grande, Mato Grosso do Sul, Brasil. Cad Saúde Pública 2019; 35 Suppl 3:e00086819.^,1010. Pícoli RP, Carandina L, Ribas DLB. Saúde materno-infantil e nutrição de crianças Kaiowá e Guaraní, Área Indígena de Caarapó, Mato Grosso do Sul, Brasil. Cad Saúde Pública 2006; 22:223-7..

This study aimed to analyze the birth weight of indigenous children using data from the First National Survey of Indigenous People’s Health and Nutrition in Brazil (henceforth, “National Survey”), conducted in 2008-2009 ⁵5. Coimbra Jr. CEA, Santos RV, Welch JR, Cardoso AM, Souza MC, Garnelo L, et al. The First National Survey of Indigenous People's Health and Nutrition in Brazil: rationale, methodology, and overview of results. BMC Public Health 2013; 13:52.. This is the first study to address indigenous children’s birth weight based on a nationwide representative sample.

Methodology

The National Survey assessed the nutritional status and other health indicators of 6,128 indigenous children aged less than 5 years (93.1% of the planned sample), employing a representative probabilistic sample of the indigenous population residing in 113 Brazilian villages from four geopolitical regions: North, Northeast, Central, and South/Southeast ⁵5. Coimbra Jr. CEA, Santos RV, Welch JR, Cardoso AM, Souza MC, Garnelo L, et al. The First National Survey of Indigenous People's Health and Nutrition in Brazil: rationale, methodology, and overview of results. BMC Public Health 2013; 13:52.. Data on birth weight, birthplace, and type of birth were collected from children’s health records or vaccination cards. Further details about the study methodological design can be found in Coimbra Jr. et al. ⁵5. Coimbra Jr. CEA, Santos RV, Welch JR, Cardoso AM, Souza MC, Garnelo L, et al. The First National Survey of Indigenous People's Health and Nutrition in Brazil: rationale, methodology, and overview of results. BMC Public Health 2013; 13:52..

For analyses, we considered the cut-off points for low birth weight < 2,500g, normal birth weight from 2,500g to 4,499g, and macrosomia ≥ 4,500g.

Birthplace was classified as “village” or “health unit” (hospitals, maternity wards, and indigenous health units).

Statistical analysis was performed considering the complex sampling design. Mean birth weights and their respective standard deviations (SD) were calculated according to region, sex, type of birth, and birthplace. The chi-square test was used to analyze differences in proportions, and Kruskal-Wallis and Mann-Whitney U tests in means, considering sample design and data normality. All tests were conducted considering a 95% significance level. Analyses were performed using IBM SPSS Statistics for Windows, version 21.0 (https://www.ibm.com/).

The study was approved by the Brazilian National Commission for Research Ethics (n. 256/2008) and the Brazilian National Indian Foundation.

Results

We found no records on birth weight for 26.7% of the 6,128 sampled children in the researched documents. The North region had the highest number of children without birth weight data (51%), while the other regions presented less than 30% of missing data, ranging from 18.3% (Northeast) to 26.7% (South/Southeast) (Table 1). Although missing data on birth weight had no significant difference regarding sex, we found important differences according to birthplace and type of birth. In the North, 78.5% (n = 1,035) of births without data on birth weight occurred in villages, whereas this value was only 21.2% in the South/Southeast. Cesarean deliveries performed in the South/Southeast and Northeast presented high percentages of missing birth weight data (15.2% and 10.1%, respectively).

The mean birth weight for the 3,994 children analyzed (65.2% of the total sample) was 3,201g (SD ± 18.6g), regardless of sex, type of birth, and birthplace. The prevalence of low birth weight was 7.6% (n = 302). Low birth weight ranged from 7.3% in the Northeast to 7.9% in the Central. The Northeast showed the highest mean birth weight (3,264g), while the Central had the lowest (3,137g) (Table 1).

Only 0.6% of the sample (n = 18) was born with very low birth weight (< 1,500g), with an average weight of 1,223g (SD ± 103.8g). Of these, 96.3% occurred in health units and mainly in the South/Southeast (51.7% - data not shown in table). Moreover, 1% (n = 39) of the sample presented macrosomia.

The regional prevalence of low birth weight among children born in villages, where the highest percentage of data loss occurred, showed slightly higher values than that observed nationally (North: 10.3%; Central: 9.8%; Northeast: 7.5%; and South/Southeast: 9.8% - data not shown in table).

The prevalence of low birth weight was significantly higher among girls (p-value < 0.05), and boys presented significantly higher mean birth weight than girls, regardless of the region (p-value < 0.05) (Table 1).

Cesarean sections had a higher percentage of low birth weight (10.3%) than vaginal deliveries (7.2%). The average birth weight of children born by vaginal delivery was 3,198g (SD ± 19.8) - slightly, but significantly lower than those born by cesarean section, whose average birth weight was 3,222g (SD ± 30.1g; p-value < 0.001).

The percentage of low birth weight was higher for deliveries performed in villages (9.5%) than for those performed in health units (7.1%). The average birth weight for children born in health units was 3,223g (SD ± 19.7g) - slightly, but significantly higher than those born in villages, whose value was 3,120g (SD ± 32.1g; p < 0.001). Only 11 of the 2,877 births performed in health units occurred in indigenous health units, all of which in the North region (data not shown in table).

Discussion

For over half a century, low birth weight has been considered a factor strongly associated with infant mortality and a barrier for a healthy childhood. Several studies worldwide reported an association between low birth weight and lifelong disabilities, such as hearing loss, chronic lung diseases, and cognitive impairment ¹1. Wilcox AJ. On the importance - and the unimportance - of birthweight. Int J Epidemiol 2001; 30:1233-41.^,22. Blencowe H, Cousens S, Chou D, Oestergaard M, Say L, Moller A-B, et al. Born too soon: the global epidemiology of 15 million preterm births. Reprod Health 2013; 10 Suppl 1:S2..

Our study is the first nationwide investigation to address birth weight in Brazilian indigenous children. However, we were unable to access information on gestational age due to the inadequate coverage and quality of prenatal care for indigenous women in the country ⁷7. Garnelo L, Horta BL, Escobar AL, Santos RV, Cardoso AM, Welch JR, et al. Avaliação da atenção pré-natal ofertada às mulheres indígenas no Brasil: achados do Primeiro Inquérito Nacional de Saúde e Nutrição dos Povos Indígenas. Cad Saúde Pública 2019; 35 Suppl 3:e00181318., making it impossible for us to assess intrauterine growth. Another limitation is the large number of sampled children without data on birth weight. Surprisingly, we also found this deficiency in maternal and child health services affecting the indigenous population to occur in regions with better socioeconomic indicators. The South/Southeast and Northeast, for example - regions with better hospital infrastructure and more qualified health professionals than the North and Central - had high percentages of data loss regarding the birth weight of indigenous children even for deliveries performed in health units. Therefore, our data on birth weight should be interpreted critically. Given the greater data loss for children born in villages, the prevalence of low birth weight may be underestimated.

Our results show that the average birth weight of Brazilian indigenous children of both sexes, regardless of the type of delivery (3,201g), is very close to that reported by Wehby et al. ¹¹11. Wehby GL, Gili JA, Pawluk M, Castilla EE, López-Camelo JS. Disparities in birth weight and gestational age by ethnic ancestry in South American countries. Int J Public Health 2015; 60:343-51. (3,127.5g).

Based on data from the National Survey, we found slightly lower frequency of low birth weight (7.6%) among indigenous children than that observed in Brazilian children in general (8.1%) ³3. Andrade CLT, Szwarcwald CL, Castilho EA. Baixo peso ao nascer no Brasil de acordo com as informações sobre nascidos vivos do Ministério da Saúde, 2005. Cad Saúde Pública 2008; 24:2564-72.. Regarding the type of birth, data from the National Survey indicate a higher prevalence of low birth weight among indigenous children born by cesarean sections (10.3%), which tends to be observed in the general population due to the association between surgical delivery and preterm labor ⁴4. Silveira MF, Victora CG, Horta BL, Silva BGC, Matijasevich A, Barros FC. Low birthweight and preterm birth: trends and inequalities in four population-based birth cohorts in Pelotas, Brazil, 1982-2015. Int J Epidemiol 2019; 48 Suppl 1:i46-53.. We also verified a higher frequency of low birth weight among children born in villages (9.5%), which may reflect less coverage and lower quality of primary healthcare within these areas.

Our results highlight the need to improve prenatal care for indigenous women as a strategy to promote safe pregnancy and childbirth. These measures will provide more qualified information about the pregnancy evolution and, consequently, records on the birth weight of indigenous children, regardless of the place or type of birth.

Acknowledgments

The authors are grateful for the assistance offered by indigenous leaders and community members of all surveyed villages, as well as the local staff at the Brazilian National Indian Foundation (FUNAI) and Brazilian National Health Foundation (FUNASA). The administrative support provided by the staff of the Brazilian Public Health Association (Abrasco) greatly facilitated travel and financial logistics.

References

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