Investigators did demonstrate a fact seen in most treatment studies: Metronidazole is not a particularly good agent for treating BV and restoring a patient’s vaginal ecology to Lactobacillus-dominant flora. However, they failed to demonstrate that treatment of asymptomatic BV reduces the risk of preterm delivery in a general obstetric population, or to establish a causal relationship between BV and preterm labor. This did not prevent them from asserting the idea that BV is a risk factor for preterm labor.
Investigators clouded their findings further by concluding that two 2-g doses of metronidazole administered 48 hours apart were effective in 72% of cases (defined as the elimination of BV) and 55% effective in restoring Gram stain scores to the normal range, noting that this effect lasted 2 to 10 weeks or longer. In reality, this is neither elimination of BV nor restoration of a normal range of microflora, but simply an interpretation of the change in Gram stain characteristics. The results do not explain what is happening microbiologically; nor do they clarify the host response to these changing conditions. Intensive quantitative bacteriology is needed, along with research into the microbial ecopathophysiology and host response to specific bacteria, in patients with and without healthy vaginal flora.
It is important to understand vaginal microflora because, when it is altered, it can impact negatively on the patient’s health. Therefore, studies that elucidate the vaginal ecology and the relationships between various bacteria further our understanding of the microbial pathophysiology leading to infection. This, in turn, leads to development of preventive measures, thus reducing the risk for adverse outcomes in both the obstetric and gynecologic patient—especially those undergoing operative procedures.
Is labor inherently protective against infection?
Molloy EJ, O’Neill AJ, Grantham JJ, et al. Labor induces a maternal inflammatory response syndrome. Am J Obstet Gynecol. 2004;190:448–455.
- LEVEL II-3 EVIDENCE: MULTIPLE OBSERVATIONS WITH OR WITHOUT INTERVENTION; UNCONTROLLED STUDIES
Although the number of participants was relatively small, this study was well considered and constructed, investigating several immunologic responses in 5 groups of patients:
- 15 nonpregnant healthy women and 17 healthy men,
- 15 healthy women in labor at term before delivery,
- 9 women with normal term pregnancies before elective cesarean with no labor,
- 9 women before emergency cesarean section after partial labor, and
- 9 women at term before emergency cesarean section without labor.
Interestingly, researchers also observed an increase of CD11b, an adhesion molecule and marker for neutrophil activation. Increased CD11b results in greater neutrophil activity.
Investigators concluded that the rise in neutrophils and diminished apoptosis in laboring patients may be an immunologic response to potential infection associated with labor, and that this phenomenon appears to be an inherent host reaction to prevent infection. It is known that bacteria from the genital tract of laboring women ascend into the uterus and amniotic fluid and colonize the decidua, amniotic membranes, and amniotic fluid. Women subsequently delivered by cesarean section are at a greater risk of infection than women delivered vaginally.
This is an extremely important finding and the first non-observational study to explain the rise in white blood cell counts during labor. It begins to explain the differences in white blood cell counts between laboring and nonlaboring patients and should spawn further investigations of a significant problem: postpartum endometritis.
Dr. Faro reports no financial relationships relevant to this article.