Effect Of Breastfeeding Duration and Exclusivity

M.Jane Heinig, PhD, IBCLC


Duration and Exclusivity Of Breastfeeding

      Cureent US recommenations for infant feeding include exclusive breastfeeding for approximately the first 6 months and partial breastfeeding with complementary foods for 12 months or longer as desired; however, the most recent infant-feeding surveys indicate that only approximately 60% of US women initiate breastfeeding, and only approximately 29% continue to 6 months of age. Although most mothers are likely to recognize that breastfeeding is beneficial for their infants, questions may arise regarding optimal breastfeeding duration and how the introduction of other foods and fluids may affect the immunologic benefits.

       Although a great deal of research has been conducted in the past 2 decades regarding the health consequences of breastfeeding, only recently have studies been designed adequately to examine the effects of specific infant feeding practices. In addition to the prospective studies summarized in this article, several large cross-sectional surveys of maternal and infant health have included detailed questions regarding infant feeding patterns.

       Using data from the US National Maternal and Infant Health Survey, Raisler et al  examined the effect of breastfeeding dose on infant illness in the first 6 months of life. After exclusion of very low birth weight infants and those without adequate data on infant feeding , 7092 infants remained in the analyses. Breastfeeding rates were generally lower in this sample  because of the inclusion of low birth weight infants and disadvantaged populations; only 40% of mothers in the sample initiated breastfeeding and only 16% were breastfeeding at 6 months.

Only 30% of mothers fully breastfed their infants at 1 month, and less than 2% were fully breastfeeding at 6 months. Using the ratio of breastfeedings to other feedings of other foods and fluids in the infant's diets, breastfeedings dose was categorized as (1) full (all  breastfeedings), (2) most (breastfeeds > other feeds), (3) equal (breastfeeds  = other feeds), and (4) less (breastfeeds < other feeds).

Compared with infants who were not breastfed, all lavels of breastfeeding had lower odds ratios of diarrhea, cough or wheeze, and vomiting .

Full breastfeeding among children without siblings reduced the risk for OM, colds, and fever compared with other feeding groups. A doseresponse effect of breastfeeding was found for protection against diarrhea and for colds among children without siblings, suggesting that a threshold level of breastfeeding is necessary to confer protection. This result remained significant among all income groups. The presence of siblings altered the relationship between breastfeeding and colds, OM, and fever, suggesting that the stress of exposure to related pathogens carried by older siblings may be too great on infant's immune systems.

      Using data from a survey of 8501 monthers in Bristol, Baker et al found that breastfeeding for 3 or more months reduced the prevalence of wheeze and diarrhea in the first 6 months of life. Resulth remained significant after controlling for several confounders, including maternal smoking, crowded housing conditions, and the presence of siblings.

       Several of the longitudinal studies reported here indicate that protection against infections illness is greatest with greater intensity of breastfeeding even among affluent populations.    Also ,breastfeeding durations of at least 3 months are commonly associated with a reduced risk for infants' illness   ; however, few infants in these populations were breastfed intensively longer than the first 3 months, limiting the ability of the researchers to determine an optimal duration of exclusive   breastfeeding.

      Evidence is also building that breastfeeding protects infants against illness beyond weaning, as indicated by several studies that included follow-up of infants beyond the first few months of life.Given the effects of breastfeeding in priming the infant immune system, these associations are biologically plausible.

      Together, these data indicate that breastfeeding is effective in reducing the risk for illness among infants even in relatively affluent populations and that exclusive breastfeeding for at least 3 months confers greater protection than dose less intense breastfeeding for  shorter durations. As numbers of infants exclusively breastfed for 6 months increase, questions regarding how longer durations of exclusive breastfeeding affect infact health may be addressed. In the interim, most studies meeting the criteria of Bauchner et al support the importance of  breastfeeding as a means of protection against acute infectiouns illness for infants and young children.

(The Pediatric Clinic of North America)


Volume 48.Number1.February 2001