Background
How and what an infant is fed during the first year of life is fundamentally important to the prevention of childhood obesity [
1]. Whether an infant is breastfed, formula fed or mixed fed with both breast milk and infant formula (herein called formula) may affect their risk of developing obesity later in life. Many studies have found breastfeeding can reduce the risk of developing obesity later in life [
2‐
5]. However, evidence for this association remains equivocal. This may reflect study definitions and design – for example some studies have not addressed important confounding variables or have used varied definitions of the duration or exclusivity of breastfeeding. It may be that the impact of breastfeeding on weight is less obvious when infants mix fed with breast and formula milk are classified as ‘breastfed’. Another consideration is how the type of milk feeding may influence infant weight gain. Infants who experience excess or rapid weight gain in infancy are more likely to be overweight or obese in childhood [
6,
7].
The mechanisms underlying the associations between the type of milk feeding and risk of developing obesity later in life are not well understood, however, there are a number of theoretical pathways that may explain this relationship. For example, a recent study has shown a positive relationship between higher protein content formula and excess weight gain in infancy [
8] and obesity in childhood [
9]. Another study found an association between use of a commercial milk cereal drink at six months and higher body mass index at 12 and 18 months [
10]. Additionally, the domain of responsive feeding, (that is the relationship between an infant’s cues of hunger and satiety and a parent’s perception and response to these cues), are important considerations in obesity prevention [
11,
12]. Together these factors have implications for formula feeding practices which include the type of formula, the preparation of formula, the amount provided and consumed, and the way in which formula is fed, for example feeding to schedule or demand.
Despite the emerging evidence suggesting that there are modifiable formula feeding practices that may contribute to the excess weight promoting effects of formula feeding very little is known about how parents use formula to feed their infants. We know generally that parents use both formal and informal sources of information and advice to guide them in how and what to feed their infants [
13] and it appears a number of factors, such as everyday situations like a holiday or illness, and previous experience also influence these practices [
14]. Yet, we know little about which specific resources are accessed when making formula feeding decisions. This is important because information, advice and support for parents using formula has been found to be inadequate or missing completely [
15‐
17]. Recent research has found that parents feeding with formula have felt unsupported by health professionals that are meant to help and support during infant rearing, such as the midwives and maternal and child health nurses [
16‐
18]. The importance of supporting parents with high quality advice and support is underscored by the findings from a number of intervention studies. For example interventions that include professional support to promote breastfeeding for parents have been found to succeed in increasing the initiation and duration of breastfeeding [
19].
Formula feeding practices, and infant feeding in general, occurs within a family and a cultural society with expected norms and values [
20]. In many countries, including Australia, the expected norm is to breastfeed [
21]. This focus on breastfeeding has meant formula feeding is often viewed as the ‘second best’ option [
22]. On the other hand, within certain demographic and cultural groups, breastfeeding may not be the expected norm [
23]. Nevertheless, some parents using formula have reported feeling judged because of their choice to use formula [
24]. These values and norms can influence the type of advice parents receive [
23].
Considering there are formula feeding practices, for example feeding according to infant hunger and satiety cues, that may reduce the risk of excess or rapid weight gain it is crucial to understand how parents use formula to feed their infants and what factors influence their formula feeding practices. This qualitative study aims to explore parents’ formula feeding practices and the factors influencing this practice, as well as exploring the source of advice used by parents.
Discussion
This study provides insights into the use of formula and mothers’ experience of advice and support for their formula feeding practices.
Feeding in response to cues of hunger and satiety has become an important focus in obesity prevention in infancy and childhood [
28]. Previous work in the United Kingdom developing a questionnaire of maternal attitudes towards infant growth and milk feeding practices found the tin, growth and appetite as potential factors used by parents to identify how much formula to offer [
29]. However, how external cues, such as the advice on the tin or the amount of milk left in the bottle, influence parents’ perception of an infant’s appetite is unclear. The current study found that for some parents there were interactions between interpreting their infant’s cues and other factors, such as the time between feeds, the amount of milk in the bottle, or the infant finishing the bottle. This could potentially lead to the infant receiving more formula than they need. A recent laboratory based study to test the impact of the bottle as a cue for mothers found that mothers with a pressure feeding style were more responsive to their infant’s cues when feeding with a weighted opaque bottle compared when feeding with a conventional clear bottle [
30] suggesting that some parents may use bottle fullness to inform their view of their child’s satiety.
Of the few studies that have assessed how much formula infants are consuming, findings reveal that infants fed formula often consume more milk than breastfed infants and current recommendations. For example, in a study of 43 infants during the first two days of life infants fed with formula consumed significantly higher amounts of milk (over double the amount) than breastfed infants [
31]. In another more recent study fully formula fed six week old infants (
n = 319) consumed a mean of 205 ml/kg body weight/day [
32], compared to current recommendation of 150 ml/kg body weight/day. Considering these findings, parents use of ‘the bottle’ and other external cues to interpret their infant’s appetite, how this related to the infant’s cues of hunger and satiety, and if this is linked to formula consumption warrants further research.
Understanding the factors that impact on infant expression of cues and parent interpretation of cues is important [
33], particularly in formula fed infants as recent findings suggest they display fewer engagement (hunger) cues and disengagement (satiety) cues over the duration of a milk feed than breastfed infants [
12]. Previous research has also found variation in parents’ explanations of their infant’s hunger and satiety cues across the first year of life [
11]. Similarly, the current study found variation in the way parents described their infant’s hunger and satiety cues across time, with cues becoming clearer to parents as the infant aged.
Another important finding of this study is the potential impact formula manufacturers’ marketing may have on how parents use formula, particularly the brand and type they choose to use, and the way formula is made up and the amount provided. The information on the tin including marketing factors such as health claims was described as informative and influenced the choice of formula for around half of the parents in this study. Parents based their decision on what they thought was most important, yet they were unsure how to interpret the information on the tin and which pieces of information they could trust. It seems that the images and text on the tin are influential pieces of marketing. It is noteworthy that parents were exposed to formula advertising considering the current restriction of advertising formula for infants under one year old in Australia under the Marketing in Australia of Infant Formulas (MAIF) Agreement [
34]. Recent research in Australia and Italy has shown that parents are likely to interpret toddler formula advertising as infant formula advertising [
15,
35] and this is concerning because toddler formula advertising is not subject to the restrictions in place for infant formula advertising across a number of countries including the United States, Canada, the United Kingdom (UK) and Australia [
36].
Considering this environment, it is important that non-commercial sources of advice and support are available to parents using formula [
37], specifically, advice that would help parents to interpret infant formula marketing and make an informed choice, rather than relying on their own perceptions of quality (for example, Australian made or organic). This is particularly important as there is an increasingly diverse range of formula from which to choose and there may be important differences between formula brands. For example, within the formulas found on the Australian market the protein content ranges widely from 13 g/L to 19 g/L in formulas design to be used from birth [
38]. This is particularly important for obesity prevention as recent research has found formula with a low protein content may reduce excess weight gain in infancy [
8] and reduce risk of childhood obesity [
9]. Yet, as the current study shows that many parents felt there is not information or advice to help guide them.
This current study, consistent with many recent studies, has found anticipatory and ongoing guidance or advice from health professional sources for formula feeding is perceived by parents as both necessary and deficient [
17,
18,
32]. A study based in the United Kingdom also found both community and hospital based midwives were limited in their knowledge of infant formulas and these midwives acknowledged that those parents that formula feed receive less information and support than those who breastfeed [
39]. Another recent assessment of infant feeding support services in regional New South Wales, Australia, found services such as written or verbal education, and support for formula feeding were inadequate [
40]. The current study found that many parents did not discuss using formula with a health professional before they started feeding with formula. This is interesting as formula tins sold in Australia carry a label in accordance with the International Code of marketing of breast-milk substitutes [
34,
41], advising that breastfeeding is the optimal infant nutrition and that parents should seek health professional advice before using formula.
Barriers to parents consulting with health professionals highlighted in this study included the perceived haste with which formula is commenced, the perception that health professionals do not endorse formula and the easy access to other avenues of advice and support such as commercially provided information on the tin, friends, family and the internet. That parents in the current study used non-formal sources of advice regarding formula use is consistent with other studies [
13,
32]. Interestingly, in a study based in Ireland, those parents who formula fed their infant from birth tended to use more informal sources of infant feeding information than those who mixed fed [
32]. The extent to which informal information, such as from the tin and the internet influence formula feeding practice warrants further investigation.
The current discourse and practice around infant feeding guidance has a large focus on breastfeeding. Results of the current study found health professionals do not talk about formula and they pushed the ‘breastfeeding line - breast is best’. Mothers in a Scottish study exploring their postnatal experience of infant feeding, found there was a ‘perceived reluctance’ of health professionals to provide parents with information about using formula [
16]. A study of Australian antenatal classes found that health professionals focussed on breastfeeding and sometimes portrayed formula in a negative light and as potentially harmful [
42]. Additional qualitative studies with mothers making infant feeding decisions show mothers felt some pressure to breastfeed from the health systems [
18,
43]. While clearly it is vital that health professionals do support breastfeeding, in line with current global health strategy, policy and evidence base [
44,
45], this focus may result in parents not approaching health professionals while considering formula use and not seeking support while using formula. Recent research in this area has called for feeding support that is more individual to feeding style, empathetic to parents’ choices [
46], family centred [
47] and specifically provides support for formula feeding so parents do not have to rely on commercial information [
37].
The public health message of breastfeeding promotion not only influences the interaction between parents and health professionals but permeates through many sociocultural environments and into women’s self-perception of what it means to be a ‘good’ mother [
43,
48]. Failure to breastfeed or breastfeed for the duration they intended, can cause many negative emotions including feelings of guilt [
17]. The current study found that negative community perceptions of formula feeding are palpable to parents. In line with other recent research there was a sense of ‘bottle stigma’ and guilt related to using formula, which may have implications for perinatal mental health [
46]. Additionally, while breastfeeding is considered the norm in many communities, there continue to be areas where formula feeding is most common, perceived as normal and where those choosing to breastfeed may lack support with implications for the duration of breastfeeding.
Study strengths, limitations and further research
Strengths of this study include the recruitment of a mothers from across Australia which provides rich, varied viewpoints. The sample also included various infant feeding methods and lengths of breast, formula and mixed feeding allowing for a range of experiences to be explored.
A potential limitation of this study was that the interviews were conducted via telephone. Telephone interviewing removes physical cues of communication present in face to face interviews and may limit the depth of information exchanged [
49]. However, there are also strengths to the use of this methodology given telephone interviews may promote sense of anonymity which may in turn promote openness in expressing views [
49]. The use of telephone interviews also enables mothers to remain in their own environment which can make them feel more comfortable, along with offering greater flexibility in interview times and the ability to include participants not located close to the researcher [
49]. Further limitations of this study include the interviews provide only the mother’s perspective (as no fathers were interviewed) and the potential for recall bias as the interviews were conducted when the infant was aged between nine and 11 months. A final potential limitation is that mothers’ described their formula feeding practice, rather than this practice being observed.
This study has begun to address a gap in our current understanding of how formula is provided on a day to day basis to infants and if potentially weight promoting infant feeding practice are common. However, further observational studies in this area may find different results, particularly of caregiver interpretation of cues and how this influences formula feeding practice. Additionally, further research to identify what sort of support parents using formula need and any barriers to accessing support for parents using formula to feed their infant is warranted. In addition research to understand health professional practices and experience of providing information and advice about formula to parents, and if there are barriers to provided information or advice about formula and what these barriers may be.