MONDAY, June 21 (HealthDay News) -- Babies who are born
vaginally pick up different bacteria than those who are delivered
by cesarean section, potentially affecting how their immune systems
develop, a new study suggests.
The findings could provide more insight into why babies born
through cesarean sections appear to be more at risk of allergies
and asthma, researchers say. The bacteria they're exposed to at
birth may help explain the relationship, since coming into contact
with germs seems to help babies build defenses against them.
"We want to understand what the differences are and how they are important for the baby's health," said study author Maria G. Dominguez-Bello, an associate professor in the department of biology at the University of Puerto Rico.
The research is preliminary, she said, but it could help
determine whether babies will benefit by being exposed to germs at
birth that they otherwise wouldn't encounter.
While germs may sound like a bad thing, they're often beneficial
to the body.
"We are all colonized -- our skin, mouth, intestines, vagina, ears -- by bacteria that have evolved with man," Dominguez-Bello said. "We are just now starting to unveil what these bacteria are, what they do, why they are important for organs to function." Colonization means the organism is present but not causing infection
In the new study, researchers aimed to determine what types of
germs colonize the bodies of babies as they're born. (The womb
itself is free of germs, Dominguez-Bello noted.)
The researchers tested bacteria from the skin and mouths of 10
babies within a day after their birth. They also tested bacteria
from their mothers.
Those who were born vaginally clearly picked up bacteria from
their mothers since the germs matched. Those germs, which were
linked to vaginal infections, gum disease and the digestion of
milk, appear to have been acquired as they passed through the birth
"It's very clear that the moms give the bacteria to the newborn babies. The babies are like magnets," Dominguez-Bello said.
The babies born by C-section harbored germs linked to skin
infections, acne, diphtheria and food poisoning.
One theory is that it takes a little longer for babies born via
cesarean section to come into contact with germs they need to
"In order to be healthy adults, they'll be have to be colonized and end up having 10 times as many bacteria as their own cells," she said.
Dr. Athos Bousvaros, an associate professor at Harvard Medical
School, said the study appears to be valid, although it only looked
at a small number of babies over a short period of time.
"We don't know if this different colonization will persist over time," he said. Other factors -- antibiotics, genetics and breast-feeding -- may also play a role in how germs colonize babies, he pointed out.
"Pregnant moms should not be overly concerned about having a C-section based on this research," Bousvaros said. "The research does not associate this difference in colonization with the babies developing illness -- babies have been born by C-section for decades, and are generally quite healthy. As always, however, C-section should only be done if deemed medically necessary."
The study findings are published in the online edition of the
Proceedings of the National Academy of Sciences for the week
of June 21 to 25.
The U.S. National Library of Medicine has more on