Clinical Challenge

Motherisk Update: Bacterial vaginosis during pregnancy

Should we screen for and treat it?

Adrienne Einarson, RN  Gideon Koren, MD, FRCPC

ABSTRACT

QUESTION  Some of my patients have been diagnosed with bacterial vaginosis (BV) during pregnancy; some have symptoms, others do not. Should I be treating them, and if so, with what? Also, should I be screening all my pregnant patients for BV?
ANSWER  There appears to be no benefit to screening or treating pregnant women with an average risk of BV. It is not even clear that treating pregnant women at high risk of BV is beneficial. If you decide to treat, the drugs of choice are oral or intravaginal gel metronidazole or oral clindamycin. Both these drugs are safe to use throughout pregnancy.

RÉSUMÉ

QUESTION  Certaines de mes patients ont reçu un diagnostic positif de vaginose bactérienne durant la grossesse; certaines présentent des symptômes, d’autres non. Devrais-je les traiter et, dans l’affirmative, comment? De plus, faudrait-il procéder au dépistage de la vaginose bactérienne chez toutes les patientes enceintes?
RÉPONSE  Il semble n’y avoir aucun avantage à procéder au dépistage ou au traitement chez les femmes enceintes qui présentent un risque modéré de vaginose bactérienne. Il n’est même pas clair si le traitement des femmes enceintes à risque élevé de vaginose bactérienne est bénéfique. Si vous optez pour le traitement, les médicaments de choix sont le métronidazole par voie orale ou en gel intravaginal ou la clyndamycine par voie orale. L’utilisation de ces deux médicaments est sécuritaire durant toute la grossesse.

Bacterial vaginosis (BV) occurs when there is an imbalance in vaginal bacteria that results in less hydrogen peroxide–producing lactobacilli and more Gardnerella vaginalis, anaerobes, and mycoplasmata. This relatively common condition affects between 9% and 23% of all pregnant women. It differs from other vaginal infections in its unique clinical signs and symptoms and the distinctive vaginal discharge associated with it.

Patients usually complain of an itching, burning, copious white discharge; vulvar or vaginal erythema; or pain during intercourse and burning upon urination. Patients have a musty or fishy odour and a thin white vaginal discharge. Although it is generally believed to be an endogenous condition, some behavioural factors, such as use of contraceptives, use of intimate hygiene products, and smoking, are thought to be involved. Although it is not considered a true sexually transmitted infection, it does correlate with sexual activities.

Almost half of all women diagnosed have neither signs nor symptoms.1 Diagnosis is confirmed when at least three of the following four findings are present (Amsel criteria): a thin homogeneous discharge, pH > 4.5, positive results of an amine test, and presence of clue cells. Vaginal Gram stain testing is also reliable, and a report of results provides a permanent record.2

The United States Centers for Disease Control and Prevention recommend three treatments for non-pregnant women: 500 mg of oral metronidazole twice daily for 7 days, one application of 2% clindamycin cream intravaginally at bedtime for 5 days, or one or two applications of intravaginal metronidazole gel for 5 days.3 One study showed that many women tried over-the-counter remedies, such as acidophilus yogurt, vinegar douches, and boric acid. These preparations were not only ineffective, but the women often misdiagnosed the vaginal infection and, therefore, instituted inappropriate treatment.4

A meta-analysis of 19 studies concluded that BV is an important risk factor for spontaneous abortions and premature births.5 Although BV can usually be eradicated,6 no clear evidence indicates that routine treatment of BV during pregnancy decreases adverse pregnancy outcomes. Most studies found that treatment did not reduce incidence of spontaneous abortions or premature labour.7

Another report of five randomized controlled trials (RCTs) involving 1504 women found that only women with a history of preterm birth appeared to benefit from treatment.8 Another RCT of 121 women found, however, that women treated for BV had a significantly lower rate of preterm births than untreated women did (4.7% vs 10.2%).9 Does this conflicting information mean all pregnant women should be routinely screened for BV? No clear answer can be found in the literature.10

Several organizations, including the American Society of Obstetrics and Gynecology, the United States Preventive Services Task Force, the US Centers for Disease Control and Prevention, and the Canadian Task Force on Preventive Health Care, reviewed all the literature on this subject. They examined all RCTs of BV treatment that specifically measured pregnancy outcomes. Seven RCTs met the inclusion criteria for the meta-analysis. Results showed no benefit to treating women at average risk of BV. In fact, two trials of high-risk women (women with previous preterm deliveries) indicated an increased risk of preterm delivery (< 34 weeks’ gestation) in women who did not have BV but received treatment. The increased risk, however, could have been due to their history of preterm deliveries.

These researchers also found that the prevalence of BV has not been well studied; there were no population-based studies in the United States. Most of the data on prevalence came from studies of women predominantly of low socioeconomic status seen at academic centres or public hospitals in the United States. The authors summarized their findings by stating that there appears to be no benefit to screening and treating BV in the general population of pregnant women, but that some pregnant women at high risk of BV might benefit from screening and treatment.11

References

1. Gonzalez Pedraza Aviles A, Ortiz Zaragoza MC, Irigoyen Coria A. Bacterial vaginosis a “broad overview.” Rev Latinoam Microbiol 1999;41(1):25-34.
2. McGregor JA, French JI. Bacterial vaginosis in pregnancy. Obstet Gynecol Surv 2000;55(5 Suppl 1):S1-19.
3. Wang J. Bacterial vaginosis. Prim Care Update Obgyns 2000;7(5):181-5.
4. Nyirjesy P, Weitz MV, Grody MH, Lorber B. Over-the-counter and alternative medicines in the treatment of chronic vaginal symptoms. Obstet Gynecol 1997;90(1):50-3.
5. Flyn CA, Helwig AL, Meurer LN. Bacterial vaginosis in pregnancy and the risk of prematurity: a meta-analysis. J Fam Pract 1999;48(11):885-92.
6. Borisov I, Dimitrova V, Mazneikova V, Shopova E. Therapeutic regimes for treating bacterial vaginosis in pregnant women. Akush Ginekol (Sofia) 1999;38(3):14-6.
7. Carey JC, Klebanoff M, Hauth J, Hillier SL, Thom EA, Ernest JM, et al. Metronidazole to prevent preterm delivery in pregnant women with asymptomatic bacterial vaginosis. N Engl J Med 2000;342:534-40.
8. Kurkinen-Raty M, Vuopala S, Koskela M, Kekki M, Kurki T, Paavonen J, et al. A randomised controlled trial of vaginal clindamycin for early pregnancy bacterial vaginosis. Br J Obstet Gynaecol 2000;107(11):1247-32.
9. Brocklehurst P, Hannah M, McDonald H. Interventions for treating bacterial vaginosis in pregnancy. Cochrane Database Syst Rev 2000;(2):CD000262.
10. Gjerdingen D, Fontaine P, Bixby M, Santilli J, Welsh J. The impact of regular vaginal pH screening on the diagnosis of bacterial vaginosis in pregnancy. J Fam Pract 2000;49(1):39-43.
11. Guise JM, Mahon S, Aickin M, Helfand M, Peipert J, Westhoff C. Screening for bacterial vaginosis in pregnancy. Am J Prev Med 2001;20(Suppl 3):62-72.0

Do you have questions about the safety of drugs, chemicals, radiation, or infections in women who are pregnant or breastfeeding? We invite you to submit them to the Motherisk Program by fax at (416) 813-7562; they will be addressed in future Motherisk Updates. Published Motherisk Updates are available on the College of Family Physicians of Canada website (www.cfpc.ca). Some articles are published in The Motherisk Newsletter and on the Motherisk website (www.motherisk.org) also.

Motherisk questions are prepared by the Motherisk Team at the Hospital for Sick Children in Toronto, Ont. Ms Einarson is a member and Dr Koren is Director of the Motherisk Program.