Type of bacteria living in a woman's reproductive tract may contribute to premature birth.
For the second year in a row, U.S. preterm births rose in 2016. A new study suggests that the type of bacteria living in a woman's reproductive tract may contribute to premature birth.

According to the Centers for Disease Control and Prevention (CDC), one out of every ten infants are born prematurely in the United States, defined as birth before the 37th week of pregnancy. 30% of these cases are impacted by the early breaking of water, or premature rupture of membrane (PROM). As PROM is associated with an increased risk of infection for the infant, researchers have been interested in identifying possible causes.

A new study out of the Imperial College of London has found that an imbalance in vaginal bacteria may be partially to blame for a mother's water breaking early, leading to premature births.

In most healthy pregnancies, a woman's vagina is mainly colonized by the healthy bacteria, Lactobacillus spp. Lactobacillus, a friendly bacterium that lives naturally in our digestive, urinary, and genital systems, works to stop the growth of pathogenic bacteria, or "bad bacteria." When levels of Lactobacillus bacteria drop, and other levels of bacteria rise, a pregnant woman is at risk for her water breaking early.

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A PROM puts the baby at risk for infection, as the neonate is no longer protected inside the amniotic sac. Bacteria that live in the vaginal tract can now migrate upwards and to the placenta and uterus. As a result, the standard treatment has been to administer intravenous antibiotics to the mother in this situation.

Researchers have found that while this generally accepted practice is helpful to reduce infection in some women, for others, it may be quite dangerous.

In a study published this week in the journal BMC Medicine, researchers analyzed the composition of vaginal bacteria in 250 pregnant women, as well as 87 women who presented to the hospital with PROM. Utilizing swabs from the vagina, the scientists were able to evaluate the types of bacteria present in the women.

Of the 250 pregnant women, 27 had premature births. The results of the study showed a shift in the microbiota of women who experienced a PROM. Specifically, there was a drop in Lactobacillus and a rise of associated harmful bacteria such as Staphylococcus and Streptococcus.

The researchers then analyzed the vaginal microbes of women who had premature births, both before the administration of a course of erythromycin, a common antibiotic given in this situation, and after.

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The study found that for those women who already had low levels of Lactobacillus, the antibiotics were helpful, reducing the number of harmful bacteria. However, for those women who microbial makeup was predominantly Lactobacillus, the antibiotics killed off the friendly bacteria and promoted the growth of more dangerous bugs.

"This study is one of the first to show that around almost a half of pregnant women may have an unbalanced vaginal microbiota before premature rupture, providing further evidence of the role of bacteria in some cases of premature births." said study author Dr. David MacIntyre.

"Crucially, our findings identify two different groups of women with premature rupture - one group in which targeted antibiotics may be beneficial and the other in which this same treatment may actually be detrimental."

The results of the study suggest a common thread in medicine: A one-size fits all approach is not helping women.

"The aim of antibiotic treatment in PPROM is to reduce the risk of ascending infection. Our results suggest that a more personalized approach targeting only those women likely to benefit from antibiotics may prove more beneficial than the current 'one treatment fits all' approach." said lead author Dr. Richard Brown.