SciELO - Scientific Electronic Library Online

 
vol.30 número2Prevalencia del uso de chupete en lactantes amamantados y no amamantados atendidos en un hospital universitarioMemoria de las madres sobre amamantación y hábitos de succión en los primeros meses de la vida de sus hijos índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados

Articulo

Indicadores

Links relacionados

Compartir


Revista Paulista de Pediatria

versión impresa ISSN 0103-0582

Rev. paul. pediatr. vol.30 no.2 São Paulo jun. 2012

http://dx.doi.org/10.1590/S0103-05822012000200004 

ORIGINAL ARTICLE

 

Exclusive breastfeeding and factors related to early weaning: a comparative study between 1999 and 2008

 

Lactancia materna exclusiva y factores asociados a su interrupción temprana: estudio comparativo entre 1999 y 2008

 

 

Vera Lúcia Vilar de Araújo BezerraI; Amanda Leite NisiyamaII; Anna Lopes JorgeII; Rayane Marques CardosoII; Eduardo Freitas da SilvaIII; Rosana Maria TristãoIV;

Instituição: Hospital Universitário de Brasília da Universidade de Brasília (UnB), Brasília, DF, Brasil
I
Doutora em Pediatria pela Universidade Federal de São Paulo (Unifesp); Professora Titular de Pediatria na Faculdade de Medicina da UnB, Brasília, DF, Brasil
II
Graduanda em Medicina da UnB, Brasília, DF, Brasil
III
Doutor em Ciências da Saúde pela UnB; Professor Adjunto do Departamento de Estatística da UnB, Brasília, DF, Brasil
IV
Pós-doutora em Neurociências pela University College of London (UCL); Professora Colaboradora da Faculdade de Medicina da UnB, Brasília, DF, Brasil

Endereço para correspondência

 

 


ABSTRACT

OBJECTIVE: To analyze the indicators of exclusive breastfeeding (EB) in Brasilia's University Hospital (BUH) during a 10-year interval and to verify associated factors to early weaning.
METHODS: A retrospective cross-sectional study was conducted by chart review of children attending the Pediatric Clinic during 1999 and 2008. The duration of exclusive breastfeeding was categorized at four months and four months or more. Prevalence ratios for early weaning (EB<4 months) were estimated with a model of Poisson regression and robust variance. Non-parametric Mann-Whitney test was used to compare the exclusive breastfeeding duration in the studied years.
RESULTS: Among 2,173 patients, 1,443 in 1999 and 730 in 2008. There was an increase from 110.7 to 123.6 days in the duration of EB. A significant association between maternal education and early weaning was shown, with a 12.6% higher prevalence in mothers with less than eight years of schooling compared to those with 11 or more years. No other associations were found in the study.
CONCLUSIONS: Similarly to what was found in Brazilian capitals and Brasilia, there was an increase in the length of exclusive breastfeeding related to mother educational level. Nevertheless, the duration exclusive breastfeeding is still below the threshold of 180 days recommended by the World Health Organization.

Key-words: breast feeding; weaning; risk factors.


RESUMEN

OBJETIVO: Analizar los indicadores de lactancia materna exclusiva (LME) del Hospital Universitario de Brasília (HUB) los años de 1999 y 2008 e identificar factores asociados a su interrupción temprana.
MÉTODOS: Estudio retrospectivo transversal con análisis de prontuarios de niños atendidos en los años de 1999 y 2008 en el Ambulatorio de Pediatría, Crecimiento y Desarrollo del HUB. La duración del LME fue dicotomizada en hasta cuatro meses y cuatro meses o más, estimando las razones de prevalencia para el desmame precoz (LME<4 meses), utilizando un modelo de regresión de Poisson con variancia robusta y la prueba no paramétrica de Mann-Whitney para comparación del tiempo de LME en los años estudiados.
RESULTADOS: Se analizó un total de 2.173 pacientes, siendo 1.443 referentes al año de 1999 y 730 al año de 2008. Se observó un incremento del 110,7 para 123,6 días en la duración del LME de 2008 respecto a 1999 (p<0,0001). El desmame temprano fue el 12,6% superior en madres con hasta siete años de estudio que en madres con 11 o más años de estudio (p<0,05). Los demás factores analizados no mostraron relación estadísticamente significativa con desmame temprano.
CONCLUSIONES: Así como encontrado en las capitales brasileñas y Distrito Federal, se verificó incremento en lo que se refiere a la duración del LME, asociado positivamente al nivel educacional materno más elevado. Conviene subrayar, sin embargo, que la duración observada en el estudio todavía es inferior a los 180 días recomendados por la Organización Mundial de Salud.

Palabras clave: lactancia materna; destete; factores de riesgo.


 

 

Introduction

Breast-feeding is essential to children's health and development during their first months of life(1,2). In addition to the benefits of the calorie and protein supplied, breastmilk also provides immunological protection that is particularly necessary during the first year of life(3). The literature reports that exclusively breast-fed newborn infants have a reduced risk of death from diarrhea and respiratory diseases(4), enjoy benefits in the areas of cognition(5) and motor function and also score higher on indicators of general infant health(6).

Since 2001, the United Nations Children's Fund (Unicef) and the World Health Organization (WHO) have been recommending exclusive breastfeeding (EBF) until 6 months of age and maintenance of breastfeeding combined with complementary feeding (mixed breastfeeding - MB) from 6 to 24 months or older(7).

A series of Brazilian studies(8) covering the country's state capitals and the Distrito Federal (DF) reported increases in breastfeeding indicators from 1999 to 2008, with median EBF duration rising from 23.4 to 54.1 days and median duration of breastfeeding from 295.9 to 341.6 days. It was also notable that mean EBF prevalence among children less than 4 months rose from 35.5% in 1999 to 51.2% in 2008, with a variation of 15.7% for Brazil as a whole and 10% in the DF taken alone. Notwithstanding, it was found that despite the fact that breastfeeding rates have improved significantly in the Brazilian state capitals and the DF, they are still well below the targets set by the WHO, which is to a great extent the result of the heterogeneous nature of breastfeeding practices in the different regions and the federal capital.

National health policies, such as the National Breastfeeding Policy (1981) and the Baby Friendly Hospital Initiative (1990), or even local policies, such as the lactation counseling provided at the Breastfeeding Encouragement Center and Milk Bank at the Hospital Universitário de Brasília, are designed to achieve the objective of having a positive impact on the quality and duration of breastfeeding for all children, with special emphasis on those at risk of premature weaning.

The objective of this study was to analyze the behavior of indicators of exclusive breastfeeding and its prevalence in data for 1999 and 2008 from the Hospital Universitário de Brasília (HUB), which is a public tertiary hospital, and to test for significant associations between demographic and clinical factors and early cessation.

 

Methods

This was a retrospective cross-sectional study analyzing medical records for children seen in 1999 and 2008 at the HUB's pediatric growth and development clinic. There were 1,996 separate consultations in 1999 and 920 in 2008. Medical records were selected from these datasets if they met the following inclusion criteria: a) age of patient from 0 to 1 year on day of consultation; b) No contraindications or other factors preventing breastfeeding, such as severely malformed infants or seropositive mothers; c) Medical record available in the hospital archives and no missing or incomplete information that could introduce doubt about any of the study variables. On this basis, 95 medical records from 1999 and 13 from 2008 were excluded for not meeting the age criterion, 10 from 1999 and 15 from 2008 because there were contraindications to breastfeeding; and, finally, 448 from 1999 and 162 from 2008 were excluded either because the records were missing from the archives or because they were missing information.

All of the remaining medical records that met the inclusion criteria described above were then analyzed for the following variables: year of consultation (1999 of 2008); location of town of origin (a) Plano Piloto, Lago Sul or Lago Norte, b) other administrative regions, c) the state of Goiás, d) other locations); age of mother (<20, 20–24, 25–29, 30–34 or > 35 years); mother's educational level (<7, 8–10 or > 11 years in education); number of prenatal consultations (0, 1–4, 5–9, > 10 consultations); number of previous pregnancies (0, 1–3, 4–6, >6 pregnancies); type of delivery (normal or cesarean); sex of infant; gestational age – prematurity (25 to 37 weeks), full term (38 to 42 weeks), overdue (over 42 weeks); and type of infant feeding.

Data on feeding were collected from the medical records and classified according to WHO criteria(9) as EBF, MB or artificial feeding (AF). Children were classified as on EBF when fed only breastmilk with no other liquids whatsoever, such as water, teas and juices, or other foods with the exception of medications; they were defined as on MB if fed breastmilk and other solid, semisolid or liquid foods, including non-human milks; and were defined as on AF if they were not being fed any breastmilk.

A statistical analysis was conducted using SAS 9.2 in order to compare breastfeeding estimates for the two years and to test for possible associations between maternal and infant factors and EBF duration. Exclusive breastfeeding duration for 1999 and 2008 was compared using the Mann-Whitney nonparametric test. The effects on exclusive breastfeeding of infant's sex and gestational age, mother's age and educational level, type of delivery, number of prenatal consultations and number of previous pregnancies were investigated using a Poisson regression model with robust variance(10).

Data collection for this study was initiated after the project had been approved by the Research Ethics Committee at the Faculty of Health.

 

Results

All of the medical records that met the inclusion criteria were analyzed, making a total of 2,173 medical records: 1,443 from 1999 and 730 from 2008. Table 1 shows the distribution of the children according to the variables investigated.

The Mann-Whitney nonparametric test was used to compare EBF duration for the two years and showed that duration was statistically greater in 2008 than in 1999 (p<0.0001), having increased from 110.7 days to 123.6 days.

Exclusive breastfeeding duration was dichotomized as less than 4 months or 4 months or more. Table 2 shows the distribution of the variables by exclusive breastfeeding duration and Table 3 shows prevalence ratios for early weaning according to the same factors, calculated using multivariate Poisson regression. There was a statistically significant relationship (p<0.05) between year of consultation and prevalence of early weaning, which was 23.6% higher in 1999 than in 2008. Maternal educational level was also associated with prevalence of early weaning, since this was 12.6 % higher among mothers with less than 7 years' study than among those who had spent 11 years or more in education.

 

 

In this study the factors infant's sex, mother's age, gestational age, type of delivery, number of prenatal consultations and number of previous pregnancies had no statistical relationship with early weaning.

 

Discussion

This retrospective study aimed to investigate temporal trends in breastfeeding at the HUB from 1999 to 2008. However, since this is not a multicenter study, its external validity is open to question. Additionally, the fact that the patients were seen at the hospital in their first, second, fourth, sixth, eighth, tenth and twelfth months of life means that behaviors that were adopted during intervals between consultations could be subject to memory bias on the part of the people taking the children to the consultations.

The optimum duration of EBF is a topic that has been debated a great deal and the advantages of 6 months' duration with relation to 4 months still merit increased precision and applicability(7). In this study a 4-month cut-off was used as an indicator of premature cessation since before 2001 the WHO recommended 4 to 6 months, so this was the parameter that was available for comparison of premature cessation during both years studied (1999 and 2008). Factors possibly associated with EBF duration were also analyzed, in addition to absolute duration.

The data collected show that the maternal age profiles for the two years were similar to what has been reported by other studies, with a majority of the mothers aged 20 to 29 years(11). Despite this, there was a significant change in age profile from 1999 to 2008: the percentage of mothers aged less than 24 reduced and the proportion of mothers aged over 25 increased, demonstrating a trend for mothers' ages to increase, which has previously been reported not only in the DF, but also in the state capitals(8).

Several studies have shown that maternal age was an important factor in premature weaning, including Bueno et al(12) and Espírito Santo(13), who suggested that mothers younger than 25 tend to introduce complementary foods earlier in their babies' lives. Nevertheless, this study found that maternal age was not a risk factor for premature cessation, since there was no significant difference between mothers under 20 years and the rest of the sample. This result, which is in line with the results of a study conducted in the state of Minas Gerais(14) with the same age group, indicates that this variable is dependent on others, such as the number of previous pregnancies(15), or on protective factors that are independent of mother's age, such as rooming-in or breastfeeding guidance(14).

The interval between 1999 and 2008 saw an impressive increase in maternal educational level, since in the earlier year just one quarter of mothers had studied for 11 years or more, whereas by 2008 more than half of the mothers had studied for 11 years or more. The authors of studies conducted in Brazil, such as Brunken et al(16), working in Porto Alegre, and several authors(17,18) from São Paulo, have consistently suggested that low maternal educational level is associated with early weaning and have pointed out that increases in maternal educational level promote breastfeeding and delay premature introduction of complementary foods. However, there are studies, such as those conducted by Caldeira and Goulart(19) and by Caetano et al(20), that failed to detect this association.

Another variable that the literature indicates has a positive association with breastfeeding is number of prenatal consultations. However, in contrast with what was expected, the results of this study did not reveal any influence on EBF duration, although there was a significant increase in the number of mothers who attended more than 10 consultations and a reduction in the number who attended less than five prenatal consultations. There are reports in the literature that demonstrate that during the prenatal period healthcare professionals can have a positive impact on EBF duration, through providing mothers with guidance and motivation(21,22). It is therefore open to speculation whether the scant attention that schools of medicine pay to breastfeeding(23) and the resulting lack of proper training in this area for professionals could result in poor quality consultations, which in turn fail to have an impact, leading to the absence of a significant relationship between the number of times mothers met health professionals and breastfeeding duration.

In this study maternal parity was associated with EBF duration, in contrast with what several other authors have observed. However, Venâncio et al(18) also reported that early weaning was more common among primiparous women. Meyerink and Marquis(24) suggested that that greater the number of pregnancies, the greater the mother's experience and, consequently, the longer the duration of breastfeeding for successive children. Since a significant proportion of the population studied here was primiparous, further studies should be conducted in order to elucidate this association, thereby helping to delineate a population at greater risk of early weaning and indicating subsets in which increased intervention is necessary to avert this outcome.

The results for type of delivery (cesarean or normal) agreed with studies undertaken in other Brazilian maternity units, since they did not indicate any relationship between type of delivery and duration of exclusive breastfeeding(25-27), even when the mother's post-operative status was taken into account.

The infant's sex did not have a relationship with breastfeeding duration, in contrast with results published by Pérez-Escamilla et al(28) and by Tabai et al(29), although the explanations that those authors found for their findings were related to cultural issues, which is an aspect that was not investigated in the present study.

Duration of pregnancy was not a significant factor in breastfeeding promotion (p=0.978), in line with studies conducted by Silveira et al(30) and Rocha and Leal(31). Nevertheless, it is known that even though breastfeeding is recommended for preterms, it is often delayed because neurological system immaturity and muscle hypotonia interfere with suckling, deglutition and respiration reflexes and, according to Padovani(32), the mothers of very low weight preterms suffer from more doubts and worries about breastfeeding than the mothers of babies carried to full term. Similarly, overdue babies that need intensive care also have breastfeeding delayed, which is a barrier to breastfeeding(33). Rocha and Leal(31) suggest that increased breastfeeding duration is more closely related to mothers breastfeeding correctly and believing in the efficacy of doing so than to the duration of pregnancy in itself.

The II Survey of Breastfeeding Prevalence in Brazilian State Capitals and the Distrito Federal(8), conducted by the Brazilian Ministry of Health, found that median EBF duration increased by a month, from 23.4 days (22.1–24.7) in 1999 to 54.1 days (50.3–57.7) in 2008. The results of this study relating to the EBF trend showed a significant increase in duration, rising from 110.7 days in 1999 to 123.6 days in 2008. Although this increase (12.9 days) was smaller than that observed by the Ministry of Health's survey(8), in both years absolute EBF duration in days was greater in this study.

The Ministry of Health(8) survey recorded an increase from 35.5% prevalence of EBF among children under 4 months old in 1999 to 51.2% in 2008, for the set of all Brazilian capitals plus the DF; while the rates were 50.6 and 60.6%, respectively, for the DF alone. In this study, 56.9% of children were exclusively breastfed for 4 months or more in 1999 and in 2008 the rate had risen to 70.8%. These data show that the results observed for the population seen at the HUB reinforce the Ministry of Health's findings with relation to EBF for 4 months or more. One possible hypothesis for the difference between the HUB rate and the indicators for the state capitals and the DF is that it is the result of a combination of the awareness-raising work carried out at the Breastfeeding Encouragement Center and Milk Bank at the HUB, the pediatric care provided at the hospital during the children's first year of life and the increased educational level of the mothers. These factors are capable of increasing mothers' adhesion to EBF and the effect of each of these factors should be analyzed in future studies. Provision of these types of services has been shown to be a decisive factor in the decision to practice EBF(34). Notwithstanding, it must not be forgotten that the EBF duration observed in this study is still below the 180 days recommended by the WHO.

Therefore, although higher maternal educational level is a protective factor against early cessation of exclusive breastfeeding, it is still necessary to understand other factors that are associated with good EBF practices, which is essential to enable planning of public healthcare actions involving more effective interventions, whether in hospitals and healthcare centers, or in the infants' social environments.

 

Acknowledgements

We would like to thank the technical team at the Hospital Universitário de Brasília, both at the Pediatric Growth and Development Clinic and at the Medical Archives, who made the data collection for this study possible.

 

References

1.  Cohen RJ, Brown KH, Canahuati J, Rivera LL, Dewey KG. Effects of age of introduction of complementary foods on infant breast milk intake, total energy intake, and growth: a randomised intervention study in Honduras. Lancet 1994;344:288-93.         [ Links ]

2.  Victora CG, Smith PG, Vaughan JP, Nobre LC, Lombardi C, Teixeira AM et al. Evidence for protection by breast feeding against infant deaths from infectious diseases in Brazil. Lancet 1987;2:319-22.         [ Links ]

3.  Rego JD. Aleitamento materno. São Paulo: Atheneu; 2001.         [ Links ]

4.  Victora CG, Smith PG, Vaughan JP, Nobre LC, Lombardi C, Teixeira AM et al. Infant feeding and deaths due to diarrhea. A case-control study. Am J Epidemiol 1989;129:1032-41.         [ Links ]

5.  Lucas A, Morley R, Cole TJ, Lister G, Leeson-Payne C. Breast milk and subsequent intelligence quotient in children born preterm. Lancet 1992;339:261-4.         [ Links ]

6.  Dewey KG, Cohen RJ, Brown KH, Rivera LL. Effects of exclusive breastfeeding for four versus six months on maternal nutritional status and infant motor development: results of two randomized trials in Honduras. J Nutr 2001;131:262-7.         [ Links ]

7.  World Health Organization. The optimal duration of exclusive breastfeeding. Report of an Expert Consultation. Geneva: WHO; 2001.         [ Links ]

8.  Brasil. Ministério da Saúde. Secretaria de Atenção a Saúde [Internet]. II Pesquisa de prevalência de aleitamento materno nas capitais brasileiras e Distrito Federal. Brasília: Ministério da Saúde, 2009 [cited 2009 Dec 01]. Available from: http://bvsms.saude.gov.br/bvs/publicacoes/pesquisa_prevalencia_aleitamento_materno.pdf        [ Links ]

9.  World Health Organization. Indicators for assessing breastfeeding practices. Geneva: World Health Organization; 1991.         [ Links ]

10. Zou G. A modified poisson regression approach to prospective studies with binary data. Am J Epidemiol 2004;159:702-6.         [ Links ]

11. Gigante DP, Victora CG, Barros FC. Relationship between maternal nutrition and duration of breastfeeding in a birth cohort in Southern Brazil. Rev Saude Publica 2000;34:259-65.         [ Links ]

12. Bueno MB, Souza JM, de Souza SB, Paz SM, Gimeno SG, Siqueira AA. Risks associated with the weaning process in children born in a university hospital: a prospective cohort in the first year of life, São Paulo, 1998-1999. Cad Saude Publica 2003;19:1453-60.         [ Links ]

13. Espírito Santo LC. Fatores associados à interrupção precoce do aleitamento materno exclusivo e influência do padrão de aleitamento materno no primeiro mês de vida na duração da amamentação [tese de doutorado]. Porto Alegre (RS): Universidade Federal do Rio Grande do Sul; 2006.         [ Links ]

14. Frota DA, Marcopito LF. Breastfeeding among teenage and adult mothers in Brazil. Rev Saude Publica 2004;38:85-92.         [ Links ]

15. Lima TM, Osório MM. Breast-feeding: profile and associated factors in children under 25 months of age in Northeast Brazil. Rev Bras Saude Matern Infant 2003;3:305-14.         [ Links ]

16. Brunken GS, Silva SM, França GV, Escuder MM, Venâncio SI. Risk factors for early interruption of exclusive breastfeeding and late introduction of complementary foods among infants in midwestern Brazil. J Pediatr (Rio J) 2006;82:445-51.         [ Links ]

17. Escobar AM, Ogawa AR, Hiratsuka M, Kawashita MY, Teruya PY, Grisi S et al. Breast-feeding and socioeconomic cultural status: factors that lead to early weaning. Rev Bras Saude Matern Infant 2002;2:253-61.         [ Links ]

18. Venâncio SI, Escuder MM, Kitoko P, Rea MF, Monteiro CA. Frequency and determinants of breastfeeding in the state of São Paulo, Brazil. Rev Saude Publica 2002;36:313-8.         [ Links ]

19. Caldeira AP, Goulart EM. Breastfeeding in Montes Claros, Minas Gerais: a representativesamplestudy. J Pediatr (Rio J)2000;76:65-72.         [ Links ]

20. Caetano MC, Ortiz TT, Silva SG, Souza FI, Sarni RO. Complementary feeding: inappropriate practices in infants. J Pediatr (Rio J) 2010;86:196-201.         [ Links ]

21. Vieira GO, Almeida JA, Silva LR, Cabral VA, Santana Netto PV. Breast feeding and weaning associated factors, Feira de Santana, Bahia. Rev Bras Saude Matern Infant 2004;4:143-50.         [ Links ]

22. Melo AM, Cabral PC, Albino E, Moura LM, Menezes AE, Wanderley LG. Knowledge and attitudes on breastfeeding among mothers of first-born babies in Recife, Pernambuco. Rev Bras Saude Matern Infant 2002;2:137-42.         [ Links ]

23. Bueno LG, Teruya KM. The practice of breastfeeding counseling. J Pediatr (Rio J) 2004;80 (Suppl 5):S126-30.         [ Links ]

24. Meyerink RO, Marquis GS. Breastfeeding initiation and duration among low-income women in Alabama: the importance of personal and familial experiences in making infant-feeding choices. J Hum Lact 2002;18:38-45.         [ Links ]

25. Barros FC, Victora CG. Breastfeeding and diarrhea in Brazilian children. New York: Demographic and Health Surveys Further Analysis Series; 1990.         [ Links ]

26. Weiderpass E, Barros FC, Victora CG, Tomasi E, Halpern R. Incidence and duration of breast-feeding by pattern of delivery: a longitudinal study in Southeastern Brazil. Rev Saude Publica1998;32:225-31.         [ Links ]

27. Carrascoza KC, Costa Júnior AL, Moraes AB. The early weaning and extended breastfeeding influent factors. Estud Psicol (Campinas) 2005;22:433-40.         [ Links ]

28. Pérez-Escamilla R, Lutter C, Segall AM, Rivera A, Treviño-Siller S, Sanghvi T. Exclusive breast-feeding duration is associated with attitudinal, socioeconomic and biocultural determinants in three Latin American countries. J Nutr 1995;125:2972-84.         [ Links ]

29. Tabai KC, Carvalho JF, Salay E. Breast feeding and weaning in two rural communities of a Brazilian town (Piracicaba-SP). Rev Nutr 1998;11:173-83.         [ Links ]

30. Silveira RB, Albernaz E, Zuccheto LM. Factors associated with the initiation of breastfeeding in a city in the south of Brazil. Rev Bras Saude Matern Infant 2008;8:35-43.         [ Links ]

31. Rocha AM, Leal I. Aleitamento materno: Uma questão em aberto. Actas do 7º Congresso Nacional de Psicologia da Saúde; 2008 Jan 31-Feb 2; Porto, Portugal. p. 65-8.         [ Links ]

32. Padovani FH. Indicadores emocionais de ansiedade, disforia e depressão e verbalizações maternas acerca do bebê, da amamentação e da maternidade em mães de bebês nascidos pré-termo de muito baixo peso, durante a hospitalização do bebê e após a alta, comparadas a mães de bebês nascidos a termo [tese de doutorado]. Ribeirão Preto (SP): Universidade de São Paulo; 2005.         [ Links ]

33. Nascimento MB, Issler H. Breastfeeding in premature infants: in-hospital clinical management. J Pediatr (Rio J) 2004;80 (Suppl 5):S163-72.         [ Links ]

34. Chaves RG, Lamounier JA, César CC. Factors associated with duration of breastfeeding. J Pediatr (Rio J) 2007;83:241-6.         [ Links ]

 

 

Endereço para correspondência:
Vera Lúcia Vilar de Araújo Bezerra
SHIN QL 2, conjunto 4, casa 5 – Lago Norte
CEP 71510-045 – Brasília/DF
E-mail: veralvab@unb.br

Recebido em: 31/5/2011
Aprovado em: 16/11/2011
Conflito de interesse: nada a declarar