OBJECTIVE: To evaluate whether vaginal flora is altered by antibiotic exposure and associated with a risk of preterm birth, particularly among women with initially normal vaginal flora.
METHODS: This was a secondary analysis of a randomized trial of metronidazole and erythromycin for the prevention of preterm birth among women with a positive fetal fibronectin test. Vaginal swabs for Nugent Gram stain score were collected for classification of bacterial vaginosis before and after antibiotic exposure and read at a central laboratory. Change in Nugent score was assessed for women with (score 7 or higher) or without (score lower than 7) bacterial vaginosis. Linear regression analysis evaluated whether change in Nugent score was associated with preterm birth.
RESULTS: Two hundred women without and 69 women with bacterial vaginosis had Gram stain performed before and after antibiotic therapy. Median Nugent score for all women declined from 4.0 to 2.0 after antibiotic therapy (P<.001). Nugent score declined both for those without (from 2.0 to 1.5, P=.11) and, more dramatically, those with bacterial vaginosis (from 8.0 to 3.0, P<.01). The components of the Nugent score that were affected by antibiotic exposure were similar among women with and without bacterial vaginosis. Antibiotic exposure and the change in Nugent score were unrelated to preterm birth among bacterial vaginosis-negative women.
CONCLUSION: Antibiotic exposure is not associated with preterm birth and does not worsen Nugent score among women with normal vaginal flora and positive fetal fibronectin.
LEVEL OF EVIDENCE: II
Among pregnant women with normal flora and positive fetal fibronectin, antibiotic exposure does not increase the risk of preterm birth or worsen Nugent score.
From the Department of Obstetrics and Gynecology of Brown University, Providence, Rhode Island; the University of Alabama at Birmingham, Birmingham Alabama; the University of Texas at San Antonio, San Antonio, Texas; the University of Cincinnati, Cincinnati, Ohio; The Ohio State University, Columbus, Ohio; Thomas Jefferson University, Philadelphia, Pennsylvania; the University of Utah, Salt Lake City, Utah; the University of Pittsburgh, Pittsburgh, Pennsylvania; the University of Miami, Miami, Florida; and The George Washington University Biostatistics Center, Washington, DC.
*For a list of other members of the NICHD MFMU, see the Appendix online at http://links.lww.com/AOG/A220.
Supported by grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) (HD21410, HD21414, HD27869, HD27917, HD27905, HD27860, HD27861, HD27915, HD34210, HD34122, HD34116, HD34208, HD34136, HD19897, and HD36801) and does not necessarily represent the official views of the NICHD or the National Institutes of Health. A portion of the time spent on this study was supported by K12HD050108 Brown University Women's Health Reproductive Health Research Career Development Program and by K23 HD062340-01 (B.A.). In the original trial, fetal fibronectin assays were provided at no cost by Adeza Biomedical, Sunnyvale, CA.
The authors thank Allison Northen, MSN, RN, for protocol development and coordination between clinical research centers, Elizabeth Thom, PhD, for protocol and data management and statistical analysis, and Robert Goldenberg, MD, for protocol development and oversight.
The study findings were previously reported in part as a poster presentation at the 57th Annual Meeting of the Society for Gynecologic Investigation, March 25–27, 2010, Orlando, Florida.
Dr. Spong, Associate Editor of Obstetrics & Gynecology, was not involved in the review or decision to publish this article.
Corresponding author: Brenna Anderson, MD, MSc, 101 Dudley Street, 3rd Floor, Providence, RI 02905; e-mail: firstname.lastname@example.org.
Financial Disclosure The authors did not report any potential conflicts of interest.