Does Bacterial Vaginosis Contribute to Preterm Labor?


Over the past several years, scientific studies from several sources have linked bacterial vaginosis (BV) with premature labor 1-3.


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Over the past several years, scientific studies from several sources have linked bacterial vaginosis (BV) with premature labor 1-3. In fact, evidence of a causal relationship between the relatively common vaginal infection and one of the mysteries of modern obstetrics was significant enough to suggest that health-care providers should monitor even asymptomatic pregnant women for BV, and/or prescribe low-grade antibiotics for a certain period during gestation.

However, a 2000 study by Carey et al for the National Institute of Child Health and Human Development (NICHD) found that a group of women who received an antibiotic between their 16th and 23rd weeks of pregnancy, and their second treatment between their 24th and 29th weeks of pregnancy were not any less likely to experience premature labor than a group of women who received a placebo during the same period 4.

What is Bacterial Vaginosis?

Bacterial vaginosis is an infection of the vagina that has various symptoms including a milky discharge and foul odor. It has many causes, and can be (but is not always) sexually transmitted. It is thought to occur in pregnancy partly due to the hormonal changes that may contribute to the imbalance of vaginal flora. 

Anecdotal Evidence?

While the most recent statistical data suggests that treating BV in pregnancy may not prevent preterm labor, my personal experience with preterm labor and BV provides an interesting case study that may support monitoring for infection in some instances.

In my 28th week of gestation, I went to my prenatal check-up in the morning. I had expected the usual routine even though I had been having some "tightenings" in my abdomen, as well as some thin, runny discharge that looked slightly different from the normal abundance that can accompany pregnancy. Still, I assumed that I would report these things to my doctor, and after a cursory examination, he would assure me that everything would be just fine.

In reality, my thankfully thorough obstetrician took a specimen of the discharge and performed a cervix check. I don't know precisely what he was thinking, but I was sure I was simply being hypersensitive, since my last pregnancy had ended with a 918-gram 26-weeker. In fact I believe I even asked the doctor if he was just humoring me when he began the exam.

As I was beginning to decide whether or not I thought something was wrong, the obstetrician returned to the room. He informed me that I had bacterial vaginosis and that I was a centimeter dilated. He directed me to the hospital for monitoring. He handed me a prescription for Flagyl, and sent me on my way. Unfortunately, I delivered Levi Thomas in the early evening, after anti-tocolytic drugs failed to stop my labor.

Inevitably, the topic of discussion at some point turned to why I went into labor at 28 weeks. There were and still are several theories, and like many mothers in my shoes, we will probably never know definitively why I delivered another baby 3 months early. However, I personally believe that Levi's early arrival was due to a combination of incompetent cervix and BV.

I couldn't determine the incompetent cervix factor until that condition was diagnosed during my 4th pregnancy, but the reason I held onto the BV contribution was that Levi was born septic, and no other infection was present. Yet, the team of physicians caring for me was reluctant to pin the day's events on BV, stating that many women contract the infection during pregnancy but don't go on to deliver prematurely. It should be noted however that Levi's neonatologist believed BV was the contributing factor. Once I learned that incompetent cervix probably played a role, I theorized that because I was dilated and effaced, the bacteria were able to penetrate the cervix and irritate the uterus enough to cause contractions. If a normal pregnant woman develops BV, perhaps the mucous plug in her cervix is able to protect the uterus and amniotic sac from the invading bacteria. This is, of course, my personal theory. I am not a medical professional nor have I studied this information scientifically.

In my 4th pregnancy, prior to the diagnosis of incompetent cervix (and prior to my eventual dilation and effacement), I also contracted BV. I was extremely diligent in monitoring my body's signs and signals and was therefore diagnosed and treated early. I had no contractions, and thanks to a cerclage and bedrest, I did not have another preemie. I also remained free from BV because I followed standard precautions and stayed abstinent throughout the rest of the pregnancy.


Certainly, my experiences neither prove that BV contributes to preterm labor, nor can they necessarily give credence to the "monitor/treat everyone" method of prevention. However, it is possible that a modified version is reasonable: long-term prescription of low-grade antibiotics, or laboratory examination of vaginal discharge even when symptoms are not present, may be a deterrent for women with a history of preterm labor. In early 2001, the National Institutes of Health solicited applications for a grant to study the link between various infections, including BV, and premature labor. It is hoped that significant evidence will point to a clear link between BV and premature labor; and, consequently lead to recommendations for a standard of care that may indeed decrease the number of babies who enter the world before they are ready to be born.




1 Association between Bacterial Vaginosis and Preterm Delivery of a Low-Birth-Weight Infant. New England Journal of Medicine, 1995. Hillier Sharon L. et al.

2 Low Birthweight in Minority and High-Risk Women. Final Report of the Low-Birthweight Patient Outcomes Research Team (Abstract). Agency for Health Care Policy and Research, Rockville, MD.

3 The Preterm Prediction Study: Significance of Vaginal Infections. American Journal of Obstetrics & Gynecology, 1995. Meis PJ, Goldenberg RL, Mercer B, et al. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network.

4 Metronidazole to Prevent Preterm Delivery in Pregnant Women With Asymptomatic Bacterial Vaginosis. New England Journal of Medicine, 2000. Carey JC, Klebanoff MA, Hauth JC, et al National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units

About the Author

Jennifer Kragt is The Preemie Place's Business and Marketing Manager. She is married to Gary and the mother to 4 beautiful son; Elijah, Jonah (former 26 weeker), Levi (former 27 weeker) and Micah. Having had three difficult pregnancies, Jennifer has a special interest in perinatology and high risk pregnancies.

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