Exclusive breastfeeding is recommended for all newborns for ∼6 months, followed by continued breastfeeding plus complementary foods for at least a year.1 This recommendation results in numerous beneficial health outcomes for the mother and infant, lasting well beyond the period of breastfeeding.2 Recent evidence provides the scientific basis to explain the importance of an exclusive breast milk diet and draws attention to the potential health risks of early infant formula supplementation.3 By using observational studies and controlling for confounding variables, in-hospital formula feeding (IHFF) has been linked to a greater than twofold increase in early cessation of breastfeeding.4–6 However, authors of these previous studies may be criticized for using inappropriate methods because the outcome of breastfeeding duration is also related to demographic and other characteristics that influence in-hospital formula use. This issue was addressed by McCoy and Heggie7 in a study published in this issue of Pediatrics using an eloquent study design with propensity scoring. In propensity scoring, covariates (such as those listed in Table 1 of McCoy and Heggie's article7 ) are used to assign a numerical prediction of the exposure, in this case IHFF, to measure the effect of this exposure on the outcome of breastfeeding cessation.8 This model is useful to estimate a potentially causal link in an observational study design in which the exposure or intervention, IHFF, cannot be randomly assigned or blinded in a trial. Furthermore, they tested their prediction using both an unmatched and matched sample to explore how comprehensive their inclusion of potential confounding variables were, which was illustrated by the overlap of propensity scores in the prediction variable (IHFF) and control variable (exclusive breastfeeding).7 Finally, they conducted an additional analysis controlling for excessive weight loss defined by weight loss nomograms9 in the newborn as another predictor for IHFF, although some of these infants may have been exclusively breastfed in the birth hospital.
By using the conservative approach, controlling for weight loss, the hazard ratio for weaning over the first year was 2.5 (95% confidence interval 1.9–3.4). A hazard ratio was derived from a multivariable analysis over time to estimate the hazard or risk of weaning. This result is analogous to previous estimates by using more traditional observational studies, such as the Infant Feeding Practices Study II, in which early exclusive breastfeeding was associated with an increased likelihood of mothers achieving their breastfeeding goals (adjusted odds ratio 2.3; 95% confidence interval 1.8–3.1).5
Although the majority of medically indicated reasons for IHFF, other reasons for IHFF, and reasons for shortening the duration of breastfeeding is included in the model, there may be exceptions. One example is hypoglycemia, which may have been included in the model under “infant medical complications.” Given an increased prevalence of maternal obesity with either gestational or type 2 diabetes (both of the latter conditions were included in the model), neonatal hypoglycemia has become a more common problem. When the mother’s own milk is not available to correct the glucose level, alternatives include glucose gel, donor milk, and infant formula.10–13
Maternal conditions such as obesity (as a dichotomous variable BMI ≥30 vs <30), previous breast surgery, infertility, polycystic ovarian syndrome, and breast anomalies may lead to difficulties in establishing and maintaining sufficient milk supply as well as affect duration of continued breastfeeding.14 Many of these conditions lead to suboptimal intake by the infant and would be captured by the more conservative estimate that includes excessive weight loss in the model. However, some of these conditions may affect duration of breastfeeding yet may not be revealed until after the period of initial weight loss, especially for smaller newborns.
Strategies to overcome breastfeeding difficulties and offset the need for supplementation include effective policies and a supportive environment such as the World Health Organization’s Ten Steps to Successful Breastfeeding and skilled professionals able to manage early establishment of breastfeeding (Supplemental Table 1).15–17 Cultural, racial, and ethnic factors are also potential nonmedical reasons for breastfeeding supplementation, and yet support for exclusive breastfeeding among all cultures may reflect health care practitioners’ implicit bias.18 The Baby-Friendly Hospital designation is one strategy to offset systemic bias and racism in breastfeeding care.19 The implications of widely variable rates of IHFF suggest the need for a call to action on providing equitable breastfeeding care to protect the exclusivity of breastfeeding. Quality improvement efforts should include data tracking according to race, ethnicity, and other factors that are associated with IHFF.
Health care providers have long sought for a list of medical indications for IHFF and advice on how to identify the need.20 The article by McCoy and Heggie7 gives us a compelling reason to avoid unnecessary supplementation, but there are also significant consequences of missing suboptimal intake in the newborn.21,22 Future research should be focused on methods of identifying both women and infants at risk for suboptimal intake, biological consequences of early formula supplementation, and best methods to preserve exclusive breastfeeding or human milk feeding.
Opinions expressed in these commentaries are those of the authors and not necessarily those of the American Academy of Pediatrics or its Committees.
FUNDING: No external funding.
COMPANION PAPER: A companion to this article can be found online at www.pediatrics.org/cgi/doi/10.1542/peds.2019-2946.
POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.
FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.