Preterm Delivery Risk Linked to Vaginal Inflammatory Markers

It was previously thought babies were born completely sterile until passing through the birth canal. The discovery of bacteria in umbilical cord blood, placenta tissues, amniotic fluid and neonates first stool has changed our thinking. What is still left to question is which microbes cause increased risk of complications and which microbes are a part of normal fetal development.

Vaginal and intra uterine infections have been demonstrated to increase the risk of preterm labor and delivery. Over 150 pregnant women were evaluated in a retrospective cohort study to evaluate their amniotic microbiome and risk of preterm delivery.  Amniotic fluid of women who delivered preterm were found to contain a greater diversity of microbial DNA when compared to women who delivered at term. 1

Microbial invasion of amniotic cavity (MIAC) is found to increase risk of preterm labor and neonatal distress. 2 Bacteria, specifically mycoplasmas, are among the most often found to be present in preterm birth. The difficulty lies in the ability to detect such infections as they are often subclinical and require specialized techniques to be discovered. Rather than amniocentesis, a more non-invasive testing to evaluate for cervicovaginal protein biomarkers has been proposed. Cervicovaginal elevations in the inflammation promoting cytokine IL-6 has been linked to increased risk of MIAC, making evaluation for this pro-inflammatory maker a future part of prenatal care. 3

Vaginal colonization of pro or anti-inflammatory markers varies depending on the ethnicity of the woman. Data gathered on characteristics of women from different ethnic groups revealed Asian –Pacific Islanders overall had the lowest risk of pre term birth. They also had overall higher education and income, likely married, fewer lifetime sexual partners and less likely to use tobacco or alcohol when compared to white women with greater number of lifetime sexual partners and were found to have higher rates of smoking and alcohol use during pregnancy. Black women are found to suffer bacterial vaginosis at higher rates when compared to other ethnic groups.  Bacterial vaginal infections by N. gonorrhea and C. trachomatis among other organisms were found to be associated with preterm delivery. Black women have a premature delivery rate 2-3 times that of White and Asian-Pacific Islander women. Statistically significant demographic differences can lead to variations of vaginal microbial colonization, therefore, leading to varying risk of preterm delivery among ethnic groups. 4,5

Despite improved medical interventions to prevent and manage preterm delivery, rates in the US have remained unchanged. We need to look beyond post natal management of premature neonates and start influencing this preterm delivery rate by screening for prenatal risk factors, with research is pointing in the direction of determining the microbiological causes that influences preterm delivery risk.


  1. DiGiulio, D, Romero, R, Amogan, H, et al. Microbial Prevalence, Diversity and Abundance in Amniotic Fluid During Preterm Labor: A Molecular and Culture-Based Investigation. PLOS ONE: 2008. Available at: Accessed August 8, 2015.
  2. Combs, CA, Lapidus, J, Gravett, M, Garite, T, Lapointe, J. 82: Detection of microbial invasion of the amniotic cavity by analysis of cervicovaginal proteins in preterm labor with intact membranes. American Journal of Obstetrics and Gynecology. 2015;212(1). doi:10.1016/j.ajog.2014.10.128.
  3. Watts, HD, Krohn, MA, Hillier, SL, Eschenbach, DA. The Association of Occult Amniotic Fluid Infection With Gestational Age and Neonatal Outcome Among Women in Preterm Labor. Obstetrics & Gynecology. 1992;79(3):351–357. doi:10.1097/00006250-199203000-00005.
  4. Gibbs, R, Romero, R, Hillier, S, Eschenbach, D, Sweet, R. A review of premature birth and subclinical infection. American Journal of Obstetrics and Gynecology. 1992;166(5):1515–1528. doi:10.1016/0002-9378(92)91628-n.
  5. Shiono, PH. Birth weight among women of different ethnic groups. JAMA: The Journal of the American Medical Association. 1986;255(1):48–52. doi:10.1001/jama.255.1.48.
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