Benefits of breastfeeding: lowering the prevalence of asthma in children at high risk

In honor of National Breastfeeding Month in the US, BMC Pregnancy and Childbirth presents a new study examining the effect of exclusive breastfeeding in the first six months on a child’s risk of developing asthma. In children at high risk of developing asthma, exclusive breastfeeding can lower that risk.

Exclusive breastfeeding is known to have many health benefits for infants as they grow, including reduced risk of asthma and other respiratory and allergic conditions.  Established risk factors for asthma include family history and male sex.  Use of antibiotics during pregnancy has been suggested as an additional risk factor, but there has been less evidence to support this possibility.

In a new study published in BMC Pregnancy and Childbirth, Dr. Jun Zhang and colleagues at Shanghai Xinhua Hospital in China studied the interaction between the protective effect of breastfeeding and established risk factors.  In a case-control design, the authors interviewed the mothers of 634 children 3-12 years old diagnosed with asthma and mothers of 864 children of the same ages without asthma diagnosis or symptoms.

Even among these higher-risk categories …, exclusive breastfeeding eliminated the increased risk associated with use of antibiotics.

As expected, they found that half of the children with asthma had a family history compared to only 20% of the children without asthma.  They also found a higher prevalence of boys in the asthma group. Furthermore, they found that 7% of the asthma cases had been exposed to antibiotics during pregnancy compared to 3.5% of the controls supporting the hypothesis that antibiotic use is a risk factor for asthma in children.  The authors calculated that antibiotic use was associated with a 1.7 times increase in the risk of developing asthma.

When the authors divided the cases and controls by whether or not the children had been exclusively breastfed (EBF) for the first six months of life, the increased risk associated with use of antibiotics disappeared in the EBF group and increased to 2.6 times in the non-EBF group.

When dividing the children by sex and family history, antibiotic use was associated with a greater increased risk of asthma in boys and in those with family history (2.2 and 3.1 times higher risk respectively) than in the girls or those without family history.  Even among these higher-risk categories of antibiotics plus another risk factor, EBF eliminated the increased risk associated with use of antibiotics.

The large sample size and the diverse recruitment of the control group make this study very useful in the identification of both risk factors and protective practices for asthma.  Although antibiotics are often necessary to treat harmful infections that could seriously harm a pregnant woman or her fetus, this study highlights that potential risks need to be considered when prescribing antibiotics for less-serious infections.  Additionally, these findings call for studies to determine whether antibiotic type, duration, dosage, and time used during pregnancy affect the risks of children developing asthma.

There are growing efforts around the world to support women in breastfeeding, and the current findings showing that EBF in the first six months of life can attenuate increased asthma risk associated with antibiotic use in pregnancy can bolster these efforts.  The authors hope that these results will be used to advocate for EBF especially in China where the EBF rate is “still relatively low.”

The ways in which breastfeeding might help prevent asthma may be complex, but one possible mechanism is that breast milk could encourage the growth of “good bacteria” in the gut to promote immune development.  More research is needed to determine how the benefits provided by breast milk actually work.

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