Risk factors for early EBF cessation
Of the 19 variables tested in this study, 9 showed an association with early discontinuation of EBF, i.e., before the child completed 6 months of life. Two of these variables – limiting the number of nighttime feeds at the breast and mother partner’s appreciation for breastfeeding – had not been previously evaluated in Brazilian studies, according to information from a systematic review including only studies with representative samples and with adjustment for possible confounding factors .
Mothers who reported limiting nighttime breastfeeds presented a 58% greater risk of early EBF cessation. This finding corroborates the association found in a survey conducted in Dubai between a lower number of nighttime breastfeeds and discontinuation of exclusive and predominant breastfeeding . EBF on demand, day and night, as currently recommended, may cause physical fatigue in women, particularly those who have little or no support, and may contribute to limiting the number of breastfeeds during the night, which is also the time when prolactin levels are physiologically higher. This situation may result in a lower milk supply, and consequently, breastfeeding supplementation with other foods . In addition, limiting the number of nighttime feeds at the breast may be an indicator of difficulties with breastfeeding or even a desire of the mother to wean the child. We have no knowledge of studies other than the one conducted in Dubai that have analyzed this variable as a determinant of EBF.
Another variable that had not been previously included in Brazilian studies on determinants of EBF was mother partner’s appreciation for breastfeeding. This factor behaved as a protector against discontinuation of EBF during the first 6 months of life. Women reporting that their partners showed appreciation for breastfeeding had a 38% lower risk of presenting the outcome. This finding reinforces the role of the father or partner as a facilitator in starting and maintaining breastfeeding, by encouraging and supporting the mother .
Three other variables that had only been investigated once as possible determinants of EBF in Brazil  showed associations with the outcome in the present study, namely, guidance on breastfeeding received at the maternity hospital; presence of cracked nipples; and type of service providing prenatal care.
In the present study, women who received guidance on breastfeeding at the maternity hospital presented a 20% lower risk of abandoning EBF during the first 6 months. This behavior had already been reported for the same population; in that previous study, guidance on breastfeeding received in the hospital was associated with a 34% lower risk of discontinuation of EBF during the first month after delivery . The WHO recommends postpartum breastfeeding counseling, ranging from practical help and guidance on breastfeeding techniques to psychological support and guidance about myths and taboos . An Australian study has shown that not attending childbirth education was negatively associated with feeding any breast milk (exclusively or partially) at 6 months . Other studies also found that breastfeeding education is significantly associated with EBF practice [4, 15, 16]. Combined individual and group counseling appeared to had a greater impact than individual or group counseling alone .
The present investigation also showed that cracked nipples were associated with a 2.4-fold greater risk of discontinuing EBF within the first 6 months of life. The only Brazilian study previously investigating this variable did not find any association between nipple trauma and duration of EBF . Methodological differences between that study and ours may explain the discordant results. Whereas Santo et al. considered as nipple trauma only those lesions observed during physical breast examination in the maternity hospital (blisters, ecchymosis, marks, and cracks), in our cohort this variable was self-reported and covered the whole follow-up period. Studies conducted in other countries have emphasized that nipple trauma may increase the risk of early discontinuation of breastfeeding [14, 24]. This is a very important finding, given the magnitude of the association between cracked nipples and early discontinuation of EBF and the high incidence of nipple trauma. In a study conducted in southern Brazil, almost half of the women presented nipple trauma during the maternity stay, a condition attributed to the high prevalence of poor breastfeeding techniques . Interventions to improve breastfeeding techniques both in the hospital and at primary care settings should be considered without delay.
The situation of the variable type of prenatal care provided (private or public service) was similar to that of presence of cracked nipples. No association with duration of EBF was reported in the single previous study that evaluated this variable , even though an association was found in our cohort. Again, it is important to acknowledge methodological differences between the studies: while we evaluated the type of service where prenatal care was provided (public vs. private), França et al. focused on whether the mother had access to private facilities, not giving information about the type of service providing prenatal care .
Our pregnant women whose prenatal care was provided by public services had a 34% higher risk of abandoning EBF within the first 6 months. This finding challenges healthcare policy makers and professionals to reassess the type of prenatal care that is being delivered to women at the public healthcare system of the municipality studied. Pregnancy and delivery are unique opportunities for providing assistance to women in making decisions regarding how to feed their children – opportunities that cannot be wasted. If, on the one hand, pregnant women who use public healthcare services are at a disadvantage regarding the duration of EBF, on the other they can benefit from using hospitals accredited with the Baby-Friendly Hospital Initiative – the accreditation of public hospitals in Brazil has been on the rise. In the present study, children who were born in a Baby-Friendly Hospital had a 15% lower risk of early discontinuation of EBF. The Baby-Friendly Hospital Initiative comprises a set of standards and routines  that have been correlated with better breastfeeding rates; the initiative has been considered a determinant of the positive evolution of breastfeeding rates both in Brazil [31–33] and worldwide [3, 30].
The three other variables associated with early discontinuation of EBF in our study (low maternal educational level, mother working outside the home, and use of a pacifier) had been widely explored in both Brazilian and international studies. Maternal schooling level has been the factor most widely studied in Brazilian investigations (it was present in 18 of the 21 studies included in the systematic review) . Eleven studies showed an association between maternal schooling level and duration of EBF, and the majority found that women with lower schooling levels were at a higher risk of discontinuing EBF . Our finding that women with up to 8 years of schooling had a 34% higher risk of presenting the outcome corroborates those previous reports. A nationwide study conducted by the Brazilian Ministry of Health confirmed this association, observing that mothers with higher schooling levels exclusively breastfed for longer times . In the international setting, the association between maternal educational level and EBF also varies depending on the locality assessed. A low educational level sometimes acts as a risk factor for EBF cessation [34, 35] and sometimes as a protective factor [5, 7, 34, 35].
Mother working outside the home was the second variable most commonly evaluated in Brazil (in 17 studies) , but only three studies identified it as a determinant of shorter duration of EBF [36–38]. The greater likelihood of discontinuation of EBF observed among women who worked outside the home in our sample may have had some relationship with the work patterns observed in the city studied. Because this is a region with a high poverty rate, it is possible that more women were in informal employment in our sample (maids, cleaners, and street vendors, among other activities) and therefore did not have the right to maternity leave. In Brazil, mothers with a formal work contract have the right to 120 days of maternity leave; this period has been extended to 180 days for public employees and in some private companies . In this regard, it is important to bear in mind that the median duration of EBF in Brazil is only 1.4 month, i.e., much shorter than the duration of the maternity leave; this may explain why working outside the home was not a determinant of EBF in most studies. In our study, however, median duration of EBF was almost 3 months, a time at which many women without the right to maternity leave would already have returned to work. Similarly, other studies in different countries such as Honduras , Canada , Timor-Leste  and Ethiopia , have shown that women returning to work were less successful in maintaining EBF than their counterparts who did not return to work. In addition, in Mexico, most women interrupted EBF long before returning to work, a fact that may explain the absence of this association in that country .
Lastly, the association between pacifier use and duration of EBF also deserves to be discussed. This is the association most frequently found in the literature, and was present in 12 of the 13 Brazilian studies in which this factor was evaluated . Our study also confirmed it. The international scenario does not differ from the Brazilian one with regard to the negative influence of the use of a pacifier on duration of EBF [17, 19]. For instance, a previous Australian cohort study has found an association between introducing a pacifier before the 10th week of life and early EBF interruption . Even though this association is unequivocal, a definitive explanation for it is still lacking. Using a dummy/pacifier may reduce the frequency of breastfeeds, alter the baby’s oral dynamics , or cause nipple confusion;  it may also be a sign of difficulty with breastfeeding or the mother’s desire to wean her child .
One of the strengths of this study is its design: this was a prospective cohort with a probabilistic sample, with subjects who are representative of the city and low rate of loss to follow-up. Another merit of the study is the investigation of variables that had received little or no attention in previous literature.
The theoretical hierarchical model adopted made it possible to evaluate how variables in the same group compete with each other and how more proximal variables may mediate the effects of variables in a preceding group . For example, we observed that the magnitude of the associations substantially changed after adjustment for proximal models. Also, it was possible to show that variables in the proximal level were overall the ones most strongly associated with the outcome, and that, at a collective level, association strength increased as the proximity of variables to the outcome increased.
Among the methodological limitations of the present study, the high volume of self-reported data, which were not directly measured (e.g., mother partner’s appreciation for breastfeeding and guidance on breastfeeding received at the maternity hospital, among other variables), should be emphasized. As is the case in any investigation of determinants, the model here used was only partially capable of explaining the outcome.