Researchers tease out the potential health effects of exposure to mothers’ microbiomes at birth.
BY MAUREEN SALAMON
September 29, 2016
Anna Simonsen-Meehan felt robbed. Advised by doctors to plan a cesarean delivery for her first child, she had wanted desperately to give birth naturally. But Anna and her husband were determined not to let their son’s surgical entrance into the world rob him of the profuse coating of bacteria babies normally acquire during their passage through the birth canal.
Within a minute or so of their baby’s December 2015 birth, new father Joseph Meehan took a piece of gauze that had been soaking in his wife’s vagina just before surgery and methodically swabbed it across their son’s 8-pound body — starting with his lips, nose, and hands, then working his way down to the infant’s back and genital area.
The novel technique was an opportunity the New York City couple had been envisioning from the start of Anna’s pregnancy, since earlier uterine surgery dimmed hopes for a vaginal birth. Avidly tracking several years of research indicating that babies born naturally may have an edge over those born via C-section — with lower risks of myriad chronic health conditions such as asthma, allergies, obesity, and type 1 diabetes — the pair decided that their son should be swabbed with his mother’s vaginal microbiome.
Joseph appreciated the opportunity to get close to his son so quickly after birth — the blond-haired boy was still purple and coated with curd-like vernix from the womb — and the intensity of the moment was magnified by excitement over the potential benefits the quick wipe-down might offer their baby.
“We were trying to give him as fair a starting point as any other child,” says Joseph, 36. “The worst-case scenario is it does nothing, and I personally don’t believe that. It could be as simple as him just having the bacteria to digest his first meal … and everything downstream from that. We’re setting him up for success.”
“Since the window of opportunity is so short — within the first hour after birth — we didn’t want to miss out on that and find out later he had some medical issue as an adult because of it,” adds Anna, 38. “It felt really good to have something we could give back to him, to get back a sense of control.”
While every parent would like to set up his or her child for success, scientists are still trying to understand the effects of this procedure on C-section babies and if other factors are involved in predicting an infant’s future health and well-being.
The “Second Genome”
Long ignored, the human micro-biome — the collection of bacteria living all over and inside people’s bodies — is now being dubbed the “second genome” because of increasing awareness of its apparent impact on health and disease. The same next-generation DNA sequencing technologies that have evolved over the past dozen years, making genomic analysis far quicker and cheaper, have also fueled scientists’ efforts to identify and analyze the trillions of human bacteria — good and bad — lurking on the skin and in locales such as the gut, the ears, and the vagina.
These advances have offered microbiologists previously unheard-of opportunities to characterize these bacteria and tease out how they help humans digest food; metabolize drugs; interact with certain genes to contribute to, or protect from, disease; and even “seed” development of newborns’ immune systems to ward off chronic health ills.
“We now realize our microbiome is not just there by accident — it evolved with us,” says Gregory Buck, a professor of microbiology and immunology and director of the Center for the Study of Biological Complexity at Virginia Commonwealth University in Richmond. “We are truly looking at the second human genome. It relates to not only unhealthy conditions but healthy conditions as well, and it’s important to keep that in mind. In the last 10 years it’s become much more obvious to me and most other scientists in the field.”
With more than 1.2 million babies in the U.S. being born by C-section each year, comprising about one-third of all births, researchers say reseeding newborns with their mother’s bacteria may produce health effects that endure across generations.
Evidence is still preliminary and not entirely consistent, but a growing body of observational studies suggests babies born via C-section face higher chances of developing an array of chronic illnesses as they get older. But scientists can’t yet tell if cesarean deliveries actually cause these lasting health issues, if other factors are involved, or how much higher the risks actually are.
A research review published in June 2015 in the British Medical Journal found 20 studies linking C-sections to type 1 diabetes, 23 studies connecting them to asthma, and nine tying them to obesity. In a study of more than 320,000 babies published in the December 2015 Journal of the American Medical Association, those born by C-section had higher risks of asthma requiring hospitalization and death from all causes by age 21, but no significant differences in obesity, inflammatory bowel disease, type 1 diabetes, or cancer.
“There could be genetic factors that predispose to all of them, but they seem to have a microbial component,” explains Maria Gloria Dominguez-Bello, an associate professor at the Human Microbiome Program at New York University School of Medicine. “It’s probably a combination of risk factors,” including a higher rate of formula feeding by C-section mothers, she says.