According to the American Congress of Obstetricians and Gynecologists (ACOG), preterm labor begins with contractions of the uterus before 37 weeks of pregnancy that cause the cervix to thin out and open up. If preterm labor cannot be stopped, it leads to preterm birth. Prematurity occurs in approximately 12% of all live births in the United States, and preterm labor preceded approximately 50% of these preterm births. Preterm births account for approximately 70% of newborn deaths and 36% of infant deaths. A new study by researchers at Stanford University in Palo Alto, California has found that the composition of vaginal bacteria (bacterial flora) may indicate the risk of preterm labor. They published their findings online on August 17 in the journal Proceedings of the National Academy of Sciences.
The study authors note that bacterial flora play critical roles in health and may be especially important for mother and her developing child during pregnancy. However, despite the critical role of the human bacteria in health, our understanding of the bacterial compositional dynamics during and after pregnancy is incomplete. Therefore, they conducted a study of 49 pregnant women, 15 of whom delivered preterm. In 40 of these women, the researchers reviewed the types of bacteria present in 3,767 specimens collected weekly during pregnancy and monthly after delivery from the vagina, distal intestinal tract, saliva, and tooth/gum.
The researchers found that the bacterial composition of all four body sites remained remarkably stable during pregnancy. Lactobacillus acidophilus is a bacteria present in the mouth, intestine, and vagina. The bacteria is thought to benefit health because it produces vitamin K and lactase. The researchers found that low levels of Lactobacillus was inversely correlated with gestational age at delivery, meaning that women with low levels of the bacteria delivered earlier. In addition, the risk for preterm birth was greater for women with low levels of Lactobacillus accompanied by elevated levels of Gardnerella or Ureaplasma bacteri. This finding was confirmed with a set of 246 vaginal specimens from nine women (four of whom delivered preterm).
The investigators found that most women experienced a post-delivery disturbance in their vaginal flora characterized by a decrease in Lactobacillus and an increase in diverse anaerobic bacteria such as Peptoniphilus, Prevotella, and Anaerococcus. This disturbance was unrelated to gestational age at delivery and persisted for up to one year. The researchers noted that their findings have important implications for predicting premature labor, which is a major global health problem, and for understanding the potential impact of a persistent, altered postpartum (after delivery) vaginal flora on maternal health, including outcomes of pregnancies following short inter-pregnancy intervals.
Take home message:
A woman’s vaginal flora can be analyzed by taking a vaginal swab, staining it, and examining it under a microscope. It is a simple, inexpensive test. If the vaginal flora is abnormal, steps can be taken to correct. Due to its simplicity and low cost, it should be considered to be a routine component of prenatal lab work. Vaginal flora composition should definitely be examined in any woman who has experienced preterm labor in a past pregnancy. A course of antibiotics can alter vaginal flora, as well as the flora in other locations. Antibiotics can kill off Lactobacillus and allow a harmful bacteria to take over the territory. Thus, vaginal flora should be examined after a course of antibiotics.