Prevalência do aleitamento materno e fatores associados à interrupção da amamentação em mulheres militares

OBJETIVO: Avaliar a situacao do aleitamento materno e os fatores associados a interrupcao da amamentacao entre mulheres militares da regiao metropolitana de Belo Horizonte, Minas Gerais. METODOS: Estudo transversal com amostra de conveniencia, composta por 100 maes militares com criancas de ate 24 meses. Foram coletados dados sobre frequencia do aleitamento materno, perfil socioeconomico, carreira militar, assistencia a saude e habito materno-infantil. A analise de regressao logistica foi realizada para verificacao da associacao entre a interrupcao do aleitamento materno e as variaveis do estudo. Os testes de Mann-Whitney e t foram utilizados para apresentacao do tempo dos aleitamentos exclusivo e materno. RESULTADOS: O aleitamento materno ocorreu em 94% dos casos, com duracao mediana de 7,2 meses. Nao houve diferenca significativa do aleitamento materno entre maes militares de acordo com a patente, o nivel educacional e a atividade operacional. A analise multivariada apresentou associacao positiva entre o desmame e as variaveis: estado civil da mae (casada), informacao sobre a importância da amamentacao no pre-natal e utilizacao do leite nao humano. A variavel que se relacionou positivamente com duracao maior do aleitamento materno exclusivo foi: maes com dois filhos previos. CONCLUSOES: A atividade operacional nao interferiu na prevalencia do aleitamento materno entre maes militares. Os autores especulam que, durante o acompanhamento pre-natal, o planejamento de acoes voltadas a informacao da importância da amamentacao pode melhorar a prevalencia e a duracao do aleitamento materno nesta populacao.


Introduction
The worldwide recommendation is that all children be exclusively breastfed for the first six months of life, maintaining supplemented breastfeeding by at least 24 months (1) .This recommendation is based on the benefits of breastfeeding, such as protection against cramps in the first six months of life, as well as against respiratory and gastrointestinal infections, reducing the need for hospitalizations (2)(3)(4) .Breastfeeding satisfies an infant's nutritional needs, providing a better child development, especially in the first two years of life (5) .Regarding to long-term effects, breastfed infants show lower mean arterial blood pressure and total cholesterol, lower prevalence of overweight/obesity and type II diabetes, as well as better performance in intelligence tests (6) .
In the last two decades, both numbers of women in military service and who breastfeed have increased (7)(8)(9) .Military women that combine breastfeeding and work may have a breastfeeding experience similar to civilian working mothers, despite the specific issues of military career (9) .However, studies have shown a lower chance of six-month breastfeeding maintenance among military mothers than among civilian mothers (10) .
The characteristics of military service -as operational activity that includes policing of public places, mission requirements and organizational barriers, can make breastfeeding difficult (11) .Military career and family are institutions that require sacrifices, resources, loyalty and goals of its members.For some women, reconciling demands of military career and satisfaction of family life as a wife and mother is a challenge (12) .Socioeconomic variables and medication use during lactation are associated with the success or failure of breastfeeding, but there is still need for evaluation of the effects of these variables on the duration of breastfeeding among military mothers (13) .
Considering the lack of studies on breastfeeding among military women in Brazil and that the responsibilities and demands of a military career may interfere with breastfeeding, this study aims to investigate the prevalence of breastfeeding among a military population and the factors associated with discontinuation of breastfeeding.

Methods
This was a cross-sectional study conducted among military mothers in the metropolitan region of Belo Horizonte who had deliveries between May 2007 and September 2011.The data of interest were obtained by Instituto de Previdência dos Servidores Militares (IPSM).The study was approved by the Research Ethics Committee of Universidade Federal de Minas Gerais (UFMG) and of Hospital da Polícia Militar de Minas Gerais (HPM).
Considering that, on average, 65 deliveries are performed per year among military women in the metropolitan region of Belo Horizonte and that this study was conducted among military mothers who had deliveries between May 2007 and September 2011, a total population of 275 women was considered for sample calculation.Simple random sampling was performed, expecting a 97.9% breastfeeding frequency (14) , requiring random sample of 40 women to obtain representativeness.The study sample was composed of 100 women.We decided for a convenience sample, whereas military women are often at work in the streets.
Data collection was performed between May 2009 and September 2011.The interviews were conducted with battalions, companies, boards and agencies in support of Polícia Militar de Minas Gerais (PMMG) of the metropolitan region of Belo Horizonte, through active search.Collected data was recorded on a validated questionnaire concerning the frequency, demographic and socioeconomic characteristics of breastfeeding, military work, health care and maternal and child habits.Interviewed mothers received information regarding the content, goals, and purpose of the survey and, after the presentation and signing of the consent form, the interview was performed with guaranteed confidentiality of information.For this study, the term weaning was defined as total cessation of breastfeeding (15,16) .
The software used was SPSS, version 13.0.Characterization of data was done using a table of absolute and relative frequencies.Univariate analysis was performed using exact and asymptotic Pearson chi-square test, in order to analyze the relationship between weaning and the study variables.Variables that were statistically significant at a level of 0.20 were used on multivariate logistic regression analysis.To assess breastfeeding duration and exclusive breastfeeding, descriptive statistics were used, including mean and standard deviation (for parametric data) and medians and interquartile range (for non-parametric data), applying Mann Whitney test for comparing non-parametric samples and t test for comparing parametric data.Normality was assessed using Shapiro Wilk test.

Results
Of the 100 mothers who participated in the study, all were aged 22 years or less and had at least a high school degree, as well as a per capita income equal to or greater than military soldier's pay in Minas Gerais.Regarding the age of children, 7% had less than six months, 39% from 6 to 12 months, 54% from 12 to 24 months, among whom 53% were female and 47% male.
Among children, 94% initiated breastfeeding and 23% were exclusively breastfed.The median duration was four months for exclusive breastfeeding and 7.2 months for breastfeeding.
Among military mothers, 51 had maternity leave of four months and 49 licensed for six months.The duration of breastfeeding and exclusive breastfeeding among mothers who had leave of four months were longer, but without statistical significance on univariate analysis.
There was no significant difference between the prevalence or duration of breastfeeding according to rank, educational level or operational activities of military mothers.
According to univariate analysis, variables positively associated with weaning were: pay between five and ten minimum wages (p=0.016),mother's marital status (married) (p=0.002),information on the importance of breastfeeding during prenatal care (p=0.081), and use of nonhuman milk (p=0.019).The variables child's sex, mother's educational level, number of previous children, smoking, alcohol, complications in pregnancy, medication use, type of birth, child's permanence in hospital, father's influence, family support, and consultation before two months had no statistically significant association with the duration of breastfeeding (Table 1).
As shown in Table 2, according to multivariate analysis, variables that were positively associated with weaning, with statistical significance (p<0.05),were: mother's marital status (married) (p=0.003),information on the importance of breastfeeding during prenatal care (p=0.041), and use of non-human milk (p=0.039).
On univariate analysis, the only variable positively associated with exclusive breastfeeding was: mothers with a previous child (p=0.023).Other variables showed no association with duration of exclusive breastfeeding.On multivariate analysis, the only variable positively associated with longer duration of exclusive breastfeeding, with statistical significance, was: mothers with two previous children (p=0.04), as shown in Table 3.

Discussion
Considering the lack of studies about breastfeeding among military populations in Brazil, findings regarding   the prevalence of breastfeeding were also compared with published data from other countries.A limitation of the study was the use of a convenience sample.Thus, the sample results cannot be generalized to military populations.
The median duration of breastfeeding was 7.2 months.It was lower than the value found in Brazil, 11.2 months (17) .Among military mothers, 94% initiated breastfeeding, which is a higher value than that found on a military installation in North Carolina, in the United States, 92% (10) .The median duration of exclusive breastfeeding was four months, which is higher value than that found in Brazil, 1.8 months, and in a military hospital in Multan, Pakistan, three months (17,18) .
The duration of breastfeeding and exclusive breastfeeding was not associated with maternity leave on univariate analysis.In Oregon, in the United States, a study showed that exclusive breastfeeding declines when women return to work (19) .Research conducted with female soldiers on a military installation in the United States, in Fort Gordon, showed that reducing the license from 42 days to 30 days had no effect on the duration of breastfeeding (20) .
The mother's military rank had no effect on breastfeeding.Another study showed that officers were three times more likely to breastfeed compared to soldiers (21) .
The operational activity did not affect breastfeeding rates, because military mothers, instead of engaging in an operational activity as they return to work, are probably relocated to administrative duties during the period in which they are still breastfeeding or because the operational activity, despite its peculiar characteristics, is not a factor that interferes with the duration of breastfeeding.
Married mothers' higher chance of weaning can be justified by the belief that sexual intercourse can interfere with breastfeeding (22) .The study found that the father's influence is important in the initiation and continuation of breastfeeding (23) .Military mothers that introduced non-human milk in their infant's feeding were more likely to wean their children.Other studies have also shown that early introduction of non-human milk and baby bottle decrease the frequency of feeding and reduce duration of breastfeeding (24,25) .Mothers who received information on the importance of breastfeeding during prenatal care were negatively related to duration of breastfeeding.For better understanding of this reality, we need to check pediatricians' knowledge about breastfeeding.The fact that pediatricians in child care have training in breastfeeding is positively associated with breastfeeding (26) .According to a study conducted in Australia, it is important to know about the experiences of women concerning the advices received from health professionals, in order to know if there is consistency in the recommendations (27) .
Among the variables associated with weaning, factors related to health care and maternal and child habits were predicted in other studies and are amenable to intervention (13)(14) .
Mothers with two previous children were more likely to breastfeed exclusively, fact that coincides with the published data (13,28) .Study conducted in a military hospital in the United States showed that previous experience with breastfeeding was positively associated with breastfeeding up to six months (10) .
The knowledge of rates and factors that determine the duration of breastfeeding among military populations is an important instrument for the conception of a plan aimed at protecting and supporting breastfeeding.The study's results showed that breastfeeding rates among military populations are far from the values considered ideal and also that unmarried mothers, with more experience in breastfeeding and that did not offer non-human milk for their children, breastfed for longer.A longer duration of breastfeeding in case of mothers who received no guidance about breastfeeding during prenatal care reveals the need for a deeper study about this practice among military populations.

a
Exact Pearson chi-square test; b Asymptotic Pearson chi-square test; 95%CI: confidence interval of 95%; OR: Odds Ratio.

Table 2 -
Variables associated with weaning on multivariate analysis, metropolitan region of Belo Horizonte, Minas Gerais, from 2007 to 2011 95%CI: confidence interval of 95%

Table 1 -
Odds Ratio (OR) of variables associated with weaning among military women, metropolitan region of Belo Horizonte, Minas Gerais, from 2007 to 2011

Table 3 -
Variable associated with exclusive breastfeeding among military women on multivariate analysis, metropolitan region of Belo Horizonte, Minas Gerais, from 2007 to 2011