A Simple Technique
Dominguez-Bello’s research on the maternal microbiome is some of the most seminal in the field. She and her colleagues published a 2010 study — the first to use molecular techniques — showing that babies delivered via C-section harbor different bacteria than those born vaginally. The gut microbiome of a naturally born newborn, for instance, aligns more closely with that of his mother’s birth canal than those of C-section babies, whose microbiomes resemble their mothers’ skin.
These findings formed the basis for Dominguez-Bello’s current research, in which surgically delivered babies are swabbed with their mothers’ vaginal bacteria just after birth. The notion is still new enough that the Simonsen-Meehans’ hospital staff needed convincing they should allow the couple to do it with their son. “You want to take what from where and put it on whom?” Anna’s obstetrician asked incredulously. But Dominguez-Bello’s research lent credence to their request, and the couple is now enrolled in her study.
In a pilot study published in the February 2016 issue of the journal Nature Medicine, Dominguez-Bello and her team compared the microbiome of four C-section babies swabbed with their mothers’ bacteria with that of seven C-section infants not swabbed and seven born vaginally. More than 1,500 microbial samples were taken from the skin, anus, and mouth of all babies during their first 30 days of life.
Swabbed babies had higher levels of two types of what some have found to be, by association at least, “good” bacteria, Lactobacillus and Bacteroides. They are normally present in smaller amounts among C-section infants, while their mouth, gut, and skin microbes more closely resembled that of naturally born infants.
“It was proof of principle that if you expose a baby to maternal vaginal fluids who has not crossed the birth canal, the baby picks up vaginal bacteria,” she says. “If you are going to have an intervention that changes a natural process — in this case, a C-section — can you normalize everything else? The way I see restoration (of bacteria) is an attempt to do that.”
One Bacterium Stands Out
Fledgling research is attempting to determine how the maternal microbiome contributes to healthy babies. But while there’s much scientists still don’t know, they have learned that the bacteria in a woman’s vagina changes dramatically during pregnancy — an altered blend that then coats their babies, if born vaginally. Topping the list for some researchers is Lactobacillus, which wards off infection. But ongoing trials are also revealing a compelling variety of microbes in women’s vaginas, depending on their race, age, and other individual factors.
“Lactobacillus becomes completely dominant; it’s amazing,” Dominguez-Bello says. “There are six different compositions of microbiome in non-pregnant women … but when they get pregnant, they all become dominant in Lactobacillus.”
Why? Scientists aren’t sure, though they’re keen on the idea that evolution has made it this way for distinct reasons. “It’s not surprising it changes, but what’s interesting is how it changes,” she says. “Nature is very clever and evolution has made mechanisms that … confer advantages to the new generation.”
Part of Lactobacillus’ purpose may have to do with keeping the baby inside its mother until it’s ready to thrive on its own. In expectant mothers, low levels of Lactobacillus have been linked to a higher risk of preterm labor, which is 1.5 times more common among African-Americans than white women. Too many or too few of certain bacteria can also heighten the risk for infertility and miscarriage, in addition to preterm birth.
Buck and his fellow researchers have also identified tiny bacteria known as Mycoplasma hominis that’s particularly prevalent among women who give birth prematurely. “Preterm birth is a huge problem — about 10 percent of kids are born preterm, and 3 percent very preterm,” he notes. “There are cases where there’s a much higher frequency in some communities … and we have some ideas about why this is so. But the goal is to establish causality, and understand what the association is between the microbiome and adverse outcomes.”
Hoping for an Enormous Impact
In hopes of solving this puzzle and shedding more light on the link between new mothers’ vaginal microbiome and their children’s future health, Buck and his colleagues launched the Multi-Omic Microbiome Study – Pregnancy Initiative (MOMS-PI) in late 2013. The research, which aims to collect samples from 2,000 women during prenatal visits, will characterize pregnancy-related microbiome changes in many body areas, including the vagina, using six leading-edge “omics” technologies.
The technologies, including metagenomic rRNA gene sequencing, immunoproteomics, and interactomics, will, among other things, help characterize previously unknown bacteria and examine how bacteria interact and impact humans and their immune systems, Buck says. Funded by the National Institutes of Health’s Human Microbiome Project, which launched in 2007, the MOMS-PI effort is enrolling expectant mothers through late 2017 at Virginia Commonwealth University’s women’s and children’s clinics as well as an assortment of hospitals in Washington state.
“We are trying to do this with relatively high numbers of pregnant women and are taking a very broad approach,” Buck says. “It’s longitudinal, it’s broad, and it’s deep. I think that distinguishes us from most groups.”
Other infant microbiome research focuses not just on how infants are born, but how they’re fed, and how this issue potentially affects future health. In a 2013 study, scientists found that babies who were strictly formula-fed exhibited significant differences in intestinal bacteria — which are known to stimulate digestion as well as the immune system — compared to babies who were partially or exclusively breastfed.
When might this emerging research affect everyday medical practice? Will there come a point where every C-section baby is swabbed with its mother’s vaginal bacteria as standard care? Until long-term studies point the way, it’s still unknown how long the benefits of swabbing last. For example, researchers have also found that while babies delivered vaginally are more highly colonized by Lactobacillus in the first three months after birth, there is no difference in colonization after this period. And other factors, such as the mother’s race, age, and whether a baby is breastfed, may be just as influential for an infant’s microbiome.
