Consequences of Using Artificial Nipples in Exclusive Breastfeeding: An Integrative Review

Objective: To describe the consequences of using artificial nipples to exclusive breastfeeding. Materials and method: An integrative review carried out in the Medline ® , Cinahl, Lilacs, Web of Science, and Scopus databases to answer the following question: What are the consequences of using artificial nipples to exclusive breastfeeding? Results: 38 articles were analyzed; the analysis gave rise to two categories: neonatal factors and maternal factors influencing exclusive breastfeeding. Breastfeeding interruption was the neonatal factor most associated with the use of artificial nipples, while the level of maternal education stood out as an intervening factor in exclusive breastfeeding. Pacifiers were the dummy type more commonly mentioned, followed by feeding bottles and nipple shields. Conclusions: The consequences of offering artificial nipples to breastfed infants are mostly negative and associated with the newborn, such as early weaning, refusal to breastfeed, impaired suction technique, incorrect latch-on, interference with orofacial development, and interruption of exclusive breastfeeding. Mothers who offered artificial nipples to their infants are more likely to experience pain, nipple fissures, frustration, and reduced interaction with their infants. Contributions to the field: This review provides a better understanding of the mechanisms by which the offer of artificial nipples to newborns interferes with the initiation or maintenance of exclusive breastfeeding. This may favor planning by multidisciplinary primary medical care teams focused on promoting, protecting, and supporting breastfeeding. Objetivo: describir las consecuencias del uso de pezones artificiales para la exclusiva. Materiales y método: revisión integradora en las de , e para la siguiente cuestión: ¿ cuál es la influencia que ejerce la oferta de pezones artificiales a nacidos? Resultados: se artículos; el análisis originó dos categorías: factores neonatales y factores maternos de influencia en la lactancia exclusiva. La interrupción de la lactancia materna fue el factor neonatal más asociado al uso de pezones artificiales, mientras el nivel de escolaridad materno se de-stacó como factor interviniente en la lactancia exclusiva. El chupo fue el pezón artificial más encontrado citado, seguido del biberón y del protector mamilar. Conclusiones: las consecuencias de la oferta de pezones artificiales a los bebés em la lactancia son, en su mayoría, negativas y relacionadas con el neonato, como el desmame temprano y el rechazo al seno, la succión perjudicada, el agarre inadecuado, la interferencia en el desarrollo orofacial y la interrupción de la lactancia materna exclusiva. Las que ofrecieron pezones artificiales dolor,


Introduction
Exclusive breastfeeding is considered the gold standard in infant feeding and, when maintained for up to six months of age, provides proven benefits to the mother-infant binomial, the family, and the society (1). However, breastfeeding is strongly influenced by external factors that can lead to the interruption of exclusive breastfeeding (EBF), such as the use of dummies -pacifiers and feeding bottles, for example -, which are affordable and geographically disseminated (2).
According to the World Health Organization (WHO), EBF is the ideal form of infant nutrition up to six months of age, when solid foods are introduced as complementary feeding. The WHO has drafted the "Ten steps to successful breastfeeding" and does not recommend the use of feeding bottles and other dummies because they can potentially interfere with optimal breastfeeding practices (3).
However, women in low-and middle-income countries show poor adherence to EBF, with only 37 % of infants under six months of age being exclusively breastfed (4). In Brazil, breastfeeding (BF) is initiated but more than half of Brazilian mothers interrupt it after the first month (5). BF indicators have been stable in Brazil since 2006: -36.6 % of EBF in infants under six months of age and -52.1 % of BF in infants under two years of age (6).
It is known that the use of artificial nipples can lead to early weaning and/or reduced BF duration. However, the aspects and mechanisms by which this interference occurs must be clarified and discussed (7)(8)(9). Thus, this article aimed at describing the consequences of using artificial nipples to exclusive breastfeeding.

Type of study
Integrative literature review carried out in six steps: identifying the research question; setting inclusion and exclusion criteria; categorizing (extracting, organizing, and summarizing information); reviewing the studies; interpreting the results; and presenting the review (10).

Identifying the research question
The Population, Variables, and Outcomes strategy (Table 1) was used, which also allows for the identification of the most appropriate descriptors for the search intended in the review. So, the question is: What are the consequences of using artificial nipples to exclusive breastfeeding?

Setting the inclusion and exclusion criteria
Original studies that answered the research question and were published between 2006 and 2019 were defined as inclusion criteria. This time frame is justified by the year when Law 11.265/2006 became effective, which regulates the marketing and appropriate use of food and dummies for infants and children. Duplicate references and studies unavailable for download were excluded.

Methodology
A paired search was carried out by two authors in March 2020, in the Medical Literature Analysis and Retrieval System Online (Medline ® ), Cumulative Index to Nursing and Allied Health Literature (Cinahl), Latin American and Caribbean Health Sciences Literature (Lilacs), Web of Science, and Scopus databases. The following controlled descriptors of the Medical Subject Heading (MeSH) were used: "breastfeeding", "pacifiers", "breastfeeding", "bottles". Two crossings were implemented using the Boolean operator "AND". A total of 1,239 references were identified in the databases, with the respective crossings ( Table 2). This process resulted in 427 studies, but after excluding 37 duplicates, 390 studies were read in full. After careful reading, 247 studies were excluded for not addressing the desired population (infants aged 0 to 6 months) and 105 were excluded for not being available for download. Thirty-eight articles were included to illustrate the process of study identification, screening, eligibility, and inclusion, as shown in Figure 1.  Data were collected with the aid of a previously defined table, which included: author, year, journal/database, location, methodological design, level of evidence, and types of artificial nipples.
Subsequently, the factors influencing the use of artificial nipples on breastfeeding were summarized, found in primary studies, giving rise to two categories: neonatal factors and maternal factors.
Therefore, the articles found were numbered and the levels of evidence of the studies were categorized. Level 1: evidence resulting from a meta-analysis of multiple randomized controlled clinical trials; level 2: evidence obtained in individual studies with experimental design; level 3: evidence from quasi-experimental studies; level 4: evidence from descriptive (non-experimental) studies or with a qualitative approach; level 5: evidence from a case or experience reports; level 6: evidence-based on expert opinions.

Results
Thirty-eight articles were analyzed, initially characterized by authors, year, journal, database, location, methodological design, level of evidence, and types of dummies (according to Table 3). Pacifiers were the type of dummy more commonly found in the studies, followed by feeding bottles and nipple shields.
In the first category, the consequences that stood out were the interruption of EBF and early weaning. Regarding maternal consequences, the most prevalent were nipple fissure/pain, frustration, and reduced interaction with the newborn.

Discussion
Regarding the consequences of the use of artificial nipples to breastfeeding that are associated with the newborn, this review pointed out aspects that ranged from incorrect latch-on to longterm anatomical changes.
One of the relevant effects of the use of artificial nipples on newborns related to exclusive breastfeeding may be changes to the latch and suction pattern. Disagreement on the mechanisms by which this relationship occurs has been found in the literature, with nipple confusion being one of the aspects mentioned. Nipple confusion is a situation in which the suction pattern of the infant is modified due to the properties of the dummy (rigidity and shape of the dummy and base). Consequently, the infant may lose interest in sucking the breast because it is harder to express milk compared to artificial nipples. The nipple confusion phenomenon is not fully elucidated, as research studies indicate that suction processing in the brainstem allows healthy term infants to adapt suction in response to the specific properties of each dummy being used (1). Thus, nipple confusion is a risk newborns are exposed to when using pacifiers, feeding bottles, or nipple shields.
Another result of this study was newborns refusing to breastfeed due to the use of a pacifier or feeding bottle. Another hypothesis to explain the negative influence of pacifiers on the biomechanics of breastfeeding includes reduced demand for breast milk by the newborn, since pacifier non-nutritive sucking causes fatigue and reduced nursing sessions or breastfeeding suspension (45).
Nevertheless, the pacifier is useful in conditioning and to help preterm infants transition from enteral or gavage nutrition to oral feeding during hospitalization in intensive care units. They also benefit from the weight gain that occurs by regulating gastric motility. Pacifiers with sensory technologies are being developed to quantify the pressure of the sucking pattern and thus gain a better understanding of neurological and motor development in childhood, and explore the potential diagnostic information contained in sucking patterns under various clinical conditions (46,47).
A positive outcome of the use of artificial nipples was reduced crying and the soothing effect for infants. This effect is also reported in the literature as a causal factor for using a pacifier (48). A study with a Spanish cohort showed that co-sleeping for more than six months seems to be associated with less anxiety, less negative sucking habits (with a pacifier or feeding bottle), and a lower incidence of malocclusions (49), which indicates that other strategies can be used to reduce infant's stress, such as bouncing and breastfeeding.
As for feeding bottles, these similarly interfere with breastfeeding because of the great difference between the flow of milk that is extracted from the breast and that from the feeding bottle, making infants prefer the latter. Furthermore, breastfeeding is a complex task that requires the integration and organization of several different skills, demanding greater effort from newborns (9,50).
Regarding growth performance, partially breastfed and formula-fed newborns lag slightly behind exclusively breastfed infants in the first six months of life (51), confirming the benefits of maintaining exclusive breastfeeding.
As a result of the use of artificial nipples, this study significantly revealed the negative influence on EBF, leading to interruption and early weaning. However, even though the use of a pacifier/feeding bottle is an indicator of breastfeeding problems, a woman's desire and intention to breastfeed must be taken into account. Given its decisive character for the success of exclusive breastfeeding, this is perhaps the most important indicator of breastfeeding duration. It should be mentioned that the success of breastfeeding depends on several factors, including sociodemographic, biophysical, and psychosocial factors (52,53).
This study also found factors associated with mothers as a result of the use of artificial nipples, such as the incidence of pain, nipple fissures, frustration, and reduced interaction with their infants.
Nipple pain is related to breast trauma and infections, such as nipple fissures and candidiasis. Therefore, it has been shown that the use of pacifiers and feeding bottles is associated with a higher rate of nipple injury because it can potentially change the sucking pattern and interfere with a proper breastfeeding latch (54). In an Iranian study, pacifier use was a significant risk factor for acute mastitis in the first four weeks and between weeks 5 and 12 postpartum, being associated with duct obstruction, as the infant does not fully empty the breast, in addition to oral contamination with the transmission of pathogens to the breast (55).
An experimental study concluded that pacifiers can potentially interfere with a mother's or infant's ability to read emotional expressions. That is, the harmful effects of the use of pacifiers in newborns imply the perception of less pleasant and less stimulating emotions (56). This finding corroborates a study with binomials in Australia, where mothers with depression were evaluated. When asked to interact with their infants, they inserted a pacifier into their mouths several times, which showed difficulty in interacting (48).
Breastfeeding is not only a result of knowing the benefits and correct techniques or prior decision, but also of a woman's relationships with her social network. That said, women must get support from members of their primary network (relationship with family members, friends, or neighbors), who can help them with household chores and childcare. Taking the relationships established between breastfeeding women and the members of their social networks into account helps professionals address other aspects in addition to the biological aspects of breastfeeding (57), reaching dimensions that can lead to increased EBF duration.
As a limitation, we emphasize the inclusion of studies with a low level of evidence. The descriptors also do not restrict knowledge that is associated with the nursing field. However, the findings allow nursing professionals to broaden their knowledge regarding the risk factors for interrupting EBF due to the use of pacifiers, feeding bottles, and nipple shields.

Conclusions
The consequences of offering artificial nipples to breastfed infants are mostly negative and associated with the newborn, such as early weaning, refusal to breastfeed, impaired suction technique, incorrect latch-on, interference with orofacial development, and interruption of EBF. Reduced crying and newborn soothing are positive outcomes of the use of artificial nipples during breastfeeding.
Repercussions associated with the mother as a result of offering artificial nipples to infants include nipple fissures and pain, frustration, and reduced interaction with her infant.
It can be emphasized that offering artificial nipples to infants of any age without the risk of discontinuing EBF is not guaranteed. The discussion about whether or not to use artificial nipples does not end here, considering that their use has been normalized by the population. Nevertheless, this review made it possible to understand the mechanisms by which artificial nipples interfere with EBF, and this can support planning by multidisciplinary primary medical care teams focused on promoting, protecting, and support breastfeeding.
Conflicts of interest: None declared.