Optimal Duration of Breastfeeding

The American Academy of Pediatrics¹  and World Health Organization²  recommend breastfeeding as the optimal method of infant feeding. Multiple other medical and health professional organizations concur with this recommendation on the basis of the evidence that exclusive breastfeeding for the first 6 months of life, with continuation after the introduction of complementary solids, promotes optimal health and well-being for mothers and infants.^3–6  The reported benefits for infants are strongest in the first 12 months of life, and the benefits continue after the period of direct breastfeeding has ended.^7–12 

In this edition of Pediatrics, Christensen et al¹³  present a study demonstrating that longer duration of breastfeeding was associated with decreased risk of hospitalization for infection during the first year of life. For every extra month of any breastfeeding, adjusted analysis revealed a 4% reduced rate of hospitalization (adjusted incidence rate ratio [aIRR] 0.96; 95% confidence interval [CI] 0.93–0.99). In addition, breastfeeding for 10 to 12 months and ≥13 months reduced hospitalization for the first 2 to 3 years of life (aIRR 0.52 [95% CI 0.33–0.82] and aIRR 0.58 [95% CI 0.34–0.98], respectively). These effects were greatest for those infants who were exclusively breastfed for ≥4 months (aIRR 0.45; 95% CI 0.27–0.75). Hospitalization is an important outcome because this implies a more severe infection with resultant greater use of health care resources and economic costs.

Some previous studies examining the association between breastfeeding and infections in infancy have been limited in terms of lack of consistency in the definition of breastfeeding or by the failure to distinguish exclusive breastfeeding from any breastfeeding. Another factor that may impact the interpretation of results is that the type of feeding may be collected in a retrospective fashion, thus limiting the reliability. Christensen et al¹³  prospectively collected the breastfeeding data through weekly questionnaires. Hospitalization information came from a national registry and could be validated through medical record review.

Limitations included a nonheterogeneous patient population and mothers with higher education than the general population. Children were not able to attend public day care at <6 months of age, and day care exposure is an important risk factor for development of infection in the first year of life. In addition, the median duration of exclusive breastfeeding was only 2.1 (interquartile range: 0.7–4.4) months, whereas the median duration of any breastfeeding was 7.6 (interquartile range: 3.5–10.4) months. Furthermore, infants who were supplemented in the first week but then reverted to exclusive breastfeeding were counted as exclusively breastfed, a factor that would underestimate the results. Only 15.6% received any breastfeeding for ≥12 months. Longer durations of breastfeeding have been associated with greater protection against infectious diseases.

Authors of multiple recent meta-analyses and evidence-based reviews have reported on the evidence to support breastfeeding regarding infant health outcomes, especially concerning protection from infectious diseases, such as acute otitis media, other upper respiratory and lower respiratory infections, and gastrointestinal infections.^8–12  A meta-analysis in developed countries revealed more than a threefold increase in odds of hospitalization due to severe respiratory tract illnesses for infants who were not breastfed compared with those who were exclusively breastfed for 4 months.¹⁴  In addition, a growing body of evidence supports the important role of the intestinal microbiota in both protecting against acute infectious diseases and modulating longer-term protection against immune-mediated diseases.^15,16  Exclusive breastfeeding is associated with optimal development of the microbiota.¹⁷  Longer duration of exclusive breastfeeding is associated with reduced diarrhea-related gut microbiota dysbiosis.¹⁷  The differences in gut microbiota between exclusively breastfed and non–exclusively breastfed infants persist beyond 6 months of age,^17,18  and direct breastfeeding may play a beneficial role.¹⁹  Beyond acute infection, breastfeeding has the potential to reduce the risk for development of chronic disease in both breastfeeding mothers²⁰  and children and to decrease health care use and costs.²¹ 

In the current study from Denmark,¹³  only 9 infants (1%) were exclusively breastfed at 6 months. Currently, only 26% of all infants in the United States are exclusively breastfed for the first 6 months of life, according to the Centers for Disease Control and Prevention National Immunization Survey.²²  The World Health Organization indicates that only 1 of 3 infants is breastfed exclusively for the first 6 months of life.²  Well-developed studies with rigorous methodology and clear outcomes are important to continue to support the development of public policy on infant nutrition. It is important that this evidence also guide patient and consumer education. In the United States, the Scientific Report of the 2020 Dietary Guidelines Advisory Committee,²³  published after extensive review of select evidence, will guide the development of the 2020–2025 Dietary Guidelines for Americans. Recommendations for pregnancy, lactation, and feeding from birth to 24 months of age are provided for the first time. These include the recommendation for exclusive breastfeeding ideally for the first 6 months, followed by continued breastfeeding with the addition of nutritionally rich complementary foods. Strong evidence linking health outcomes with recommendations for breastfeeding enable consistent guidance for the health of the population.

aIRR

adjusted incidence rate ratio

CI

confidence interval