Microbial balance in vagina: Miscarriage, infertility, pre-term birth linked to vaginosis.

The Future of Humanity Rests on a Healthy Vaginal Microbiome

The Future of Humanity Rests on a Healthy Vaginal Microbiome

Health and medicine explained.
Jan. 11 2013 1:06 PM

What’s in Your Vagina?

A healthy microbiome, hopefully.

(Continued from Page 1)

And as evidence mounts that immune activation during pregnancy contributes to developmental disorders, others have examined chorioamnionitis in autism. One study of 91 preterm toddlers, also in Boston, showed a positive association. These results are highly preliminary—the study was small and used a diagnostic tool that’s only 10 percent accurate in predicting autism.

Numerous animal experiments show that inflammation during pregnancy can cause myriad problems in offspring. Simulated chorioamnionitis in pregnant sheep, for example, interferes with lung, brain, and gut development in lambs, even when the lambs are born at term. Chorioamnionitis is, in the words of a Dutch group studying it, “a multiorgan disease of the fetus.”

These are admittedly worst-case scenarios. And it’s important to remember that while vaginosis may facilitate the migration of bacteria to the uterus, the imbalance doesn’t necessarily guarantee it. More to the point, the “normal” uterus may not be sterile anyway. A healthy vaginal microbiome may not prevent microbial migration so much as promote colonization by friendly microbes.


In 2009, Finnish scientists showed that placentas from healthy children born at term were coated in DNA from lactobacilli and bifidobacteria. Somehow indigenous microbes—or at least their DNA—found their way to this inner sanctum without causing obvious problems.

In 2011, a group at Harvard found that 40 percent of placentas from more than 500 preterm children born by C-section contained culturable microbes. In this case, those placentas colonized by vaginosis-associated species were slightly inflamed. But the placentas coated with lactobacilli were not.

Australian fertility specialists have observed that fluid extracted from ovaries wasn’t sterile, either; it also contained bacteria. The study group consisted of women seeking help with conception. Women who harbored lactobacilli, the researchers found, more often had successful outcomes than those who carried other species.  

The microbes may have been introduced during the egg retrieval process, the scientists acknowledged. But they also asked, “Do we really believe that the female upper genital tract is sterile?”

“I think that there's organisms up there all the time, in healthy people,” Reid says. Some of these microbes likely ascend from the vagina. So the best approach to reproductive health will likely be proactive and preventive, not reactive and corrective. Health is not just a question of keeping the wrong bugs out, in other words, but also ensuring the right ones are present.

“The issue is, how do we promote high lactobacilli coming into pregnancy?” says Nelson. “It starts before women are thinking of conception.” In her Philadelphia cohort, for example, women who early on harbored high counts of lactobacilli were more likely to have a healthy, full-term pregnancy than those who didn’t. Similar observations have been made at the University of Washington, Seattle, among women undergoing in-vitro fertilization. The more vaginal lactobacilli at the outset, the better the outcome.

The vaginal ecosystem may contain keystone species that are especially protective. Several studies, including one by Nelson, suggest that the presence of a single lactobacillus called L. crispatus lowers the risk of both vaginosis and preterm birth. Among HIV-positive women in the United States and Kenya, meanwhile, L. crispatus seems to lessen vaginal shedding of the virus.

Which brings us to treatments. Scientists aren’t very good at treating vaginosis, it turns out. Antibiotics can beat it back in the short term, but “the norm is for it to recur,” says Craig Cohen of the University of California, San Francisco. “That’s the problem: Our tools, our treatments, are just not sufficient.”

Enter Gregor Reid, who’s at the University of Western Ontario. He has conducted two randomized trials comparing probiotics to antibiotics. In one, which was blinded and placebo-controlled, he supplemented antibiotics with probiotic lactobacilli (L. reuteri and L. rhamnosis) taken orally. This group had an 88 percent cure rate at the one-month mark, more than twice that of the group treated with antibiotics alone.

In a second, smaller study, he compared just probiotics with an antibiotic gel, both administered vaginally. With a 90 percent cure rate, probiotics alone were 40 percent more effective than antibiotics.

Then there’s “maintenance therapy”— keeping friendly microbes around once they’re established. In Italy, women who treated vaginosis with antibiotics gradually relapsed during the subsequent year. By contrast, women who also applied probiotics vaginally for six months resisted sliding back into vaginosis.

“We’re going to see more probiotics used with antibiotics,” says Barbara Cottrell of Florida State University. In the meantime, she says, “It would be nice if the CDC had a campaign: Start talking about ecosystems—that the vagina has an ecosystem—in grade school.”

Such education might help women resist marketing. I thought of Reid’s dance and presentation on the vaginal microbiome when Summer’s Eve unleashed its “Hail to the V” campaign for douching products. In one ad, a stentorian voice intoned, “It's the cradle of life … the center of civilization …  men have fought for it … even died for it.” When I described the ad to Reid, including the final exhortation to “show it a little love”—that is, to douche—he said, “I agree with everything, except for the last part.”

When I asked Cottrell about douching, she told me a story. About a decade ago, flummoxed by the high infant mortality rates in some African-American communities in the Florida panhandle—which were more than twice the rate for Caucasian infants—she began looking for explanations.

“I kept seeing bacterial vaginosis present in mothers whose babies died,” she recalls. “That’s when I started reading about vaginosis.”

She happened on statistics suggesting that one in three American women douche and that some African-American cohorts douched nearly twice as often. Showing that douching directly causes infant mortality remains difficult, yet her resulting paper, published in 2010, reads like an anti-douching manifesto.

Douching has been linked to preterm birth, an elevated risk of acquiring HIV, ectopic pregnancies, cervical cancer, and endometriosis, she points out. It may perpetuate the very condition it’s often intended to address: vaginosis. Scientists at Johns Hopkins have found that, after stopping the practice, bacterial imbalances resolved on their own.

“We recommend not doing it, that's the bottom line,” says Cottrell. If something seems amiss—a strange odor or discharge—go to the doctor. Otherwise, as womenshealth.gov says, “let your vagina clean itself.”