(RxWiki News) Following a rising trend, almost a third of all births in the United States are through caesarian section, or C-section. In many cases, these C-sections are medically necessary.
In other cases, C-sections may put babies at an unnecessary risk for health issues later in their lives.
A new study was presented at the American Academy of Allergy, Asthma and Immunology annual meeting that looked at the relationship between C-section births and later risk for developing allergies.
The study results showed that babies born through C-sections were more likely to develop allergies by age two than vaginally-delivered children.
"Consult a pediatrician about child allergies."
Christine Cole Johnson, PhD, of the Department of Public Health Sciences in the Henry Ford Health System in Detroit, Michigan, and colleagues wanted to find out if children born though C-section were more at risk for allergies.
For their study, the researchers recruited pregnant women between the ages of 21 and 49 years old attending obstetric clinics in Detroit. Researchers followed over 1,000 babies to see if they developed allergies by age two.
From these women, the researchers were able to follow 1,258 babies. After the women were enrolled in the study, they were visited at home when their babies were 1, 6 and 12 months old.
At the six-month visit, dust samples were collected to test for babies' exposure to cockroaches, dust mites, cats and dogs.
The infants were then seen for a final follow-up visit when they were 24 months old. Blood samples were collected to see if there was any blood test evidence of allergy to any of those common triggers.
The results showed that vaginally-delivered babies had no increased risk of dust allergies even if they had been exposed to dust mites in their homes.
Babies born through C-sections, however, had a 5.9 times higher risk of developing dust allergies if they were exposed to dust mites in their households, compared to vaginally-delivered babies.
They also had a similar increased risk for dog and cat allergies, though not for cockroach allergies.
C-section babies were 8.2 times more likely to have developed a dog allergy by 2 years old. They were also 1.75 times more likely to have developed a cat allergy by that time.
“As expected, detectable allergen exposure at age 6 months is associated with sensitization to that allergen at age 2 years,” said Ms. Johnson in her presentation.
“This association was only seen among infants delivered by C-section,” she said.
The researchers suggested that this increased risk of developing allergies was related to how the babies were delivered.
One explanation might be that vaginally-delivered babies get exposed to important microbiomes, or bacteria, during birth that help their immune system develop, the authors said.
“This further advances the hygiene hypothesis that early childhood exposure to microorganisms affects the immune system’s development and onset of allergies,” said Ms. Johnson at the presentation.
“We believe a baby’s exposure to bacteria in the birth canal is a major influencer on their immune system,” she said.
Without this exposure to strengthen their immune system, the authors wrote, C-section babies may be more vulnerable to developing allergic reactions.
The study was presented at the American Academy of Allergy, Asthma and Immunology annual meeting in San Antonio, Texas on February 24. The study has yet to be published in a peer-reviewed journal.
The research was funded by Henry Ford Hospital and National Institute of Allergy and Infectious Diseases.
The study authors report no conflicts of interest.