Breastfeeding and Maternal and Infant Health Outcomes In Developed Countries

Source: Ip S, Chung M, Raman G, et al. Breastfeeding and maternal and infant health outcomes in developed countries. Evidence Report/Technology Assessment No. 153. AHRQ Publication No. 07-E007. Rockville, MD: Agency for Healthcare Research and Quality. April 2007. Retrieved from http://www.ahrq.gov/downloads/pub/evidence/pdf/brfout/brfout.pdf on June 10, 2007.In this 400-page report, prepared for the Agency for Healthcare Research and Quality, the authors evaluate studies of the effects or associations of breastfeeding on various child and maternal outcomes. In a screening of over 9,000 abstracts, researchers from the Tufts-New England Medical Center Evidence-Based Practice Center identified 43 primary studies on infant health outcomes, 43 primary studies on maternal health outcomes, and 29 systematic reviews or meta-analyses to be included in the review. The primary studies were observational, randomized controlled trials, and comparative studies. The systematic reviews were included since it was not deemed feasible for all of the primary studies to be reviewed. The authors relied on the recommendations of the technical expert panel and the Office on Women’s Health to develop an approach to grade the reviews. This approach graded the meta-analyses and the primary studies included in the review as A for good, B for fair to moderate, and C for poor. “A” studies presented the least bias and the most valid results. “B” studies were susceptible to some bias but were still considered valid, and the “C” studies had significant biases that may have resulted in invalid results. In addition, screening for the meta-analyses and systematic reviews included standards for reporting for meta-analysis in observational studies in epidemiology and a checklist developed specifically for this review to evaluate the quality of the reviews of observational studies. The checklist included such questions as whether the study included an appropriate search strategy, justification for inclusion/exclusion criteria for studies, and a description of a well-defined population.The inclusion criteria required studies to have a comparative arm of formula feeding or different durations of breastfeeding, and studies had to have been conducted in developed countries. For topics that included the systematic reviews/meta-analyses, any additional primary studies were reviewed if they were published subsequent to those reviews. Studies that only included formula-fed infants were not included in the review.Definition of breastfeeding was varied across studies reviewed, so the authors elected to use the definition of exclusive breastfeeding as provided by the authors of the studies reviewed and to qualify the conclusions based on these definitions. Data were presented as a reduction in relative risk, estimated as (1–odds ratio) x 100%, along with the corresponding 95% confidence interval (CI).For the full-term infant, breastfeeding was associated with a reduced risk of acute otitis media, atopic dermatitis, gastrointestinal infections, lower respiratory tract diseases, asthma, obesity, childhood leukemia, and sudden infant death syndrome. There was a 23% (95% CI, 9–36%) reduction of otitis media when breastfeeding was compared to exclusive formula feeding. When exclusive breastfeeding for three or six months’ duration was compared to exclusive formula feeding, there was a reduction of otitis media of 50% (95% CI, 30–64%). For atopic dermatitis the authors identified only one good quality meta-analysis of 18 prospective cohort studies of full-term infants. There was a reduced risk of atopic dermatitis by 42% (95% CI, 8–59%) in children with a family history of atopy and exclusively breastfed for at least three months compared with those who were breastfed for less than three months.For gastrointestinal infections, the authors noted potential confounders that were not completely accounted for in one systematic review. However, one case-control study analyzed and rated as good found that infants who were breastfeeding had a 64% (95% CI, 26–82%) reduction in the risk of non-specific gastroenteritis compared with non-breastfeeding infants.In the area of respiratory illness, a good quality meta-analysis demonstrated a 72% (95% CI, 46–86%) reduction in the risk of hospitalization from lower respiratory tract diseases in infants less than one year of age who were breastfed exclusively for four months or more. Furthermore, an updated meta-analysis by the authors found the risk of asthma is reduced by 27% (95% CI, 8–41%) in infants breastfeeding for at least three months compared to nonbreastfed infants. If there was a family history of asthma, the risk was reduced by 40% (95% CI, 18–57%). The authors also conducted their own meta-analysis on seven case control studies and found that a history of breastfeeding reduced the risk of SIDS by 36% (95% CI, 19–49%).In three meta-analyses that were rated as good and moderate regarding methodological quality, breastfeeding was associated with a reduced risk of obesity in adolescence and adult life when compared to those not breastfed. The reduction ranged from 7% (95% CI, 1–12%) to 24% (95% CI, 14–33%).Two good quality meta-analysis and systemic review studies reached opposite conclusions regarding risk of leukemia. The authors conducted their own meta-analysis including only the good and fair quality case control studies identified in the systemic review and found breastfeeding for at least six months’ duration resulted in a 15% reduction (95% CI, 2–27%) in the risk of acute myelogenous leukemia and 19% (95% CI, 9–29%) reduction in acute lymphocytic leukemia.For the preterm infant, the authors performed a meta-analysis of four randomized controlled trials of necrotizing enterocolitis (NEC) and found an absolute risk reduction of 5%. The authors point out that while this is a small difference it is significant given the high case fatality of NEC.The outcomes where there was little or no evidence of positive outcomes related to breastfeeding included full-term and preterm cognitive development, risk of cardiovascular diseases, type 1 and 2 diabetes, and infant mortality.The authors analyzed studies focused on maternal outcomes, finding evidence that breast and ovarian cancer risk is reduced among women who breastfeed. They identified two meta-analyses of moderate methodological quality. These studies reported a reduced risk of cancer of 4.3% for every year of breastfeeding and 28% reduced risk when breastfeeding occurred for 12 months or more. This reduced risk was found primarily in pre-menopausal women. The authors found inconclusive evidence after reviewing studies that focused on return to pre-pregnancy weight, maternal type 2 diabetes, osteoporosis, and postpartum depression.The authors discussed many limitations of their review. First, they did not assess quality of primary studies included in the meta-analyses they reviewed. It is possible that some were of poor quality. In addition, internal validity and generalizability of the findings from the breastfeeding literature are constrained by the fact that most studies in the area are cohort or case-control studies that are more subject to validity threats than are prospective treatment studies. They also recognize that there is more confidence in the positive effects of the better-defined outcomes such as breast cancer, compared to asthma and nonspecific gastrointestinal infections. Finally, multiple factors with studies of obesity limit the confidence of the overall findings for this outcome.Dr. Slusser has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of a commercial product/device. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.This enormous review of the breastfeeding literature in the developed world is helpful, both for solidifying some of the benefits of breastfeeding, as well as pointing out limitations with much of the literature in the field. The AAP recommends exclusive breastfeeding for infants in the first six months of life, followed by continued breastfeeding to age one year or more.1 The AAP statement provides practical and simple ways that pediatricians can support breastfeeding: “[P]romote hospital policies and procedures that facilitate breastfeeding. Work actively toward eliminating hospital policies and practices that discourage breastfeeding (eg, promotion of infant formula in hospitals including infant formula discharge packs and formula discount coupons, separation of mother and infant, inappropriate infant feeding images, and lack of adequate encouragement and support of breastfeeding by all health care staff). Encourage hospitals to provide in-depth training in breastfeeding for all health care staff (including physicians) and have lactation experts available at all times.”Given the need to be kept abreast of the evidence that exists regarding the benefits for breastfeeding during the first year of life, this landmark report summarizes and assesses the reliability and validity of the myriad of breastfeeding studies in the peer-reviewed literature. The executive summary, not to mention the entire report, is worth having available for discussion with expectant mothers who are ambivalent about breastfeeding and want the evidence underlying the AAP recommendation that breast-feeding be offered for at least the first year of an infant’s life.