Direct From Breast Better Than Expressed Milk for Infant Weight

Bridget M. Kuehn

September 25, 2018

Babies bottle-fed breast milk gain weight more quickly than those nursed directly, but not as quickly as those fed exclusively or supplemented with formula long term, according to a study published online September 24 in Pediatrics.

Previous studies have suggested that formula feeding is associated with greater weight gains among infants than breastfeeding. But there are little data about how specific infant feeding practices, such as formula supplementation for breastfeeding babies or feeding expressed breast milk via bottle, affects weight gain. The new study shows that how babies are fed breast milk matters.

"Breastfeeding is inversely associated with weight gain velocity and BMI [body mass index]," write Meghan Azad, PhD, assistant professor of pediatrics and child health at the University of Manitoba in Winnipeg, and coauthors. "These associations are dose dependent, partially diminished when breast milk is fed from a bottle, and substantially weakened by formula supplementation after the neonatal period."

The new study followed 255 mother-infant pairs in Canada between 2009 and 2012 to document how breastfeeding and other feeding practices affected the child's weight gain and BMI at 1 year of age.

Exclusive breastfeeding at 3 months was associated with slower weight gain and lower BMI at 1 year than all other feeding regimens. Brief formula supplementation after birth or adding solid foods prior to 6 months didn't reduce these benefits.

However, later formula supplementation was associated with faster weight gain and higher BMI, adding .28 to the average BMI z score, and exclusive formula feeding later led to even greater gains (.45 BMI z score).

Infants who consumed some breast milk from a bottle also saw a small increase in weight gain (.12 BMI z score).

The study population was unusual in that 97% of the women enrolled in the Canadian Healthy Infant Longitudinal Development (CHILD) study initiated breastfeeding. They averaged 4 months of exclusive breastfeeding and reported a median of 11 months of any nursing.

In an accompanying editorial, Alison Volpe Holmes, MD, MPH, associate professor of pediatrics at the Dartmouth Geisel School of Medicine in Lebanon, New Hampshire, noted this likely reflects Canada's generous maternity leave policies, which guarantee a minimum of 15 months of paid leave and preserve women's jobs for 17 to 52 weeks of leave. By contrast, the United States guarantees no paid leave and offers only 12 weeks of job protection to a subset of individuals under the Family and Medical Leave Act.

Despite the unusually high rate of breastfeeding in the cohort, the study offers unique insights on how different feeding practices might affect infant weight gain. Holmes notes that the study is one of the first to look at specific feeding practices, such as feeding only at the breast or feeding breast milk with bottles.

The study provides reassurance for those parents introducing solid foods before 6 months in an effort to reduce the risk for food allergies, Holmes writes. It also showed that brief formula feeding in the hospital after birth didn't alter weight if mothers switched to exclusive breastfeeding.

"Our study also found that the method of feeding breastmilk matters," study author Azad said in a press release. "Feeding expressed breastmilk from a bottle appeared to have a weaker beneficial effect on infant weight compared with direct feeding at the breast, although expressed milk was still beneficial compared to infant formula."

Holmes suggests that direct feeding at the breast may lead to less weight gain than bottle feeding breast milk because it is "infant-led." It's also possible that breast milk loses some protective factors during storage, Holmes notes.

Children in the CHILD study cohort will be followed through adolescence so study investigators will be able to follow whether infant feeding practices have longer-term affects on weight.

"With this report, and more to come, pediatricians have new and better evidence to advocate for family leave and workplace support policies that protect breastfeeding mothers and infants, and improve public health," Holmes writes.

Dr Azad disclosed receiving travel expenses from Mead Johnson for a presentation about breast milk and from Medela for attending a breast milk conferences. Her coauthors and Dr Holmes have disclosed no relevant financial relationships.

Pediatrics. Published online September 24, 2018. AbstractEditorial

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