Go figure. It turns out that breastfeeding may not provide equal protection from illness to babies of both sexes. Please note that I wrote “may not.” While the study’s authors caution against doing so, many news outlets are running with the story as being conclusive, that breastfeeding is not an equal opportunity protector.

So, to all the Type-A moms, dads, and others who may be confused about the study and what it may mean, here’s a condensed report of the study’s findings.

The study was reported in the medical journal Pediatrics. (Click here to go to the study.) The authors state that breastfeeding may protect against illness transmitted in the home or by the community. Why not? After all, breast milk has been proven to prevent necrotizing enterocolitis and neonatal sepsis in high-risk infants in the neonatal ICU. However, there’s little evidence proving that breastfeeding can prevent community-acquired neonatal infections.

The study’s authors chose to study the effect of breast milk on respiratory infections, which are the most commonly diagnosed neonatal infection in infants who have been discharged from hospital nurseries. They looked at 13,224 full-term infants born at one hospital in Boston between October 1, 1990, and March 31, 1998. Of these babies, 933 were diagnosed with upper or lower nonpneumonia respiratory tract infections and who were either being exclusively breastfed or exclusively formula fed. The median age at the time of diagnosis was 22 days. The researchers chose 1,205 babies as controls.

The infants who were sick were more often:

• Born during the winter respiratory syncytial virus season
• Not only children
• A member of a socioeconomically at-risk family

An unexpected finding was that the association between breastfeeding and lower risk of neonatal respiratory tract infection was confined to the infant girls; “there was no meaningful association between breastfeeding and risk of neonatal respiratory tract infection among neonatal boys,” reported the researchers.

Only one other study has yielded similar results. In that study, researchers studied babies up to 4 months of age who also had abnormal chest radiographs and wheezing. They found that infant girls had an 11-fold increased risk of contracting a wheezing illness during their first 4 months of life if the following criteria were met:

• They were breastfed for less than a month
• They shared a room
• Their parents had respiratory issues when they were children

The Boston researchers noted that the study’s main finding (i.e., sex-specific protective association between breastfeeding and risk of neonatal respiratory infection needs to be interpreted with caution. They go on to state that their study positively supports the contention that the benefits of breastfeeding begin within the first 30 days of life.

So there you have it: once again, researchers have proven that breastfeeding leads to healthier babies. If you or someone you know is undecided about whether to nurse their baby, perhaps you could offer them verbal or tangible support during those first weeks of the baby’s life.

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