LETTER TO THE EDITOR Treatment of Bacterial Vaginosis in Pregnancy: A New Perspective To the Editor: B acterial Vaginosis (BV) is a condition in which the nor- mal balance of bacteria in the vagina (Lactobacillus spe- cies) is disrupted and replaced by an overgrowth of anaerobic bacteria, such as Gardnerella vaginalis, Mycoplasma hominis, Bacteroides species, Fusobacterium species, Mobiluncus species, and Prevotella species. In North America, it is the most common vaginal infection in women of childbearing age, and as many as 15% to 20% of pregnant women in the United States have BV 1–3 ; however, only 50% of infected women are symptomatic and complain of vaginal discharge, fishy odour, pain, itching, or burning. 3,4 BV has been associ- ated with pelvic inflammatory disease after surgical proce- dures and with preterm labour, preterm premature rupture of membranes, and microbial invasion of the amniotic cav- ity during pregnancy. 5–8 It remains unclear by which mechanism BV leads to preterm labour. According to the American College of Obstetricians and Gynecologists and the Centers for Disease Control and Prevention, the recommended treatment of BV during pregnancy is clindamycin (2% intravaginal cream 5 g at bed- time for 7 days, 300 mg orally twice daily for 7 days, or intravaginal 100-mg ovules once daily at bedtime for 3 days) or metronidazole (0.75% intravaginal gel 5 g a day for 5 days or 500 mg orally twice daily for 7 days). 9,10 Both antibiotics are effective in eradicating BV. 11 Although one of the treat- ment goals in pregnancy is to reduce the likelihood of preterm birth, there is controversy about the optimal treat- ment. 11–14 Therefore, even in women at high risk for preterm birth, it is still unclear whether screening for BV should be performed and whether or not treatment reduces the risk of preterm birth. A recent randomized controlled trial (RCT) in which second-trimester metronidazole or an equivalent placebo was given to pregnant women at high risk for preterm birth demonstrated a higher rate of preterm delivery with metronidazole. 15 This unexpected result led to an important question: Do clindamycin and metronidazole have similar efficacy in treating BV and effect on pregnancy outcome? In the January issue of JOGC, we reported the results of a meta-analysis that evaluated the effect of second-trimester antibiotics on the rate of preterm births. 16 Macrolide and clindamycin, given during the second trimester, were asso- ciated with a lower rate of preterm birth, but metronidazole was linked with a significantly higher rate of preterm deliv- ery. We can only speculate on the reasons for such differ- ence between treatments, but despite incomplete under- standing of the mechanism, we believe that in the light of these novel data, metronidazole should be avoided when- ever possible during the second trimester of pregnancy until other trials are published. What antibiotic regimen should be recommended to women with BV during pregnancy? Several studies in preg- nant and non-pregnant women have demonstrated that clindamycin’s clinical efficacy and safety are similar to those of metronidazole regimens 17,18 for the treatment of BV. Moreover, although vaginal clindamycin showed no clear benefit for pregnancy outcomes compared with placebo, the only RCT using oral clindamycin in pregnant women demonstrated a significant reduction of preterm delivery with antibiotic treatment. 19 In this trial, women who had abnormal vaginal flora (Nugent score 4–6) or BV and who were between 12 and 22 weeks’ gestation were randomized to receive either clindamycin 300 mg or placebo orally twice daily for five days. The rate of preterm birth was signifi- cantly reduced from 17.4% with placebo to 9.0% with clindamycin. Moreover, oral clindamycin was associated with a five-fold decrease in late miscarriage (delivery prior to 24 weeks), which suggests that infection-related preterm birth can potentially be prevented by systemic antibiotics. In light of the current literature, we believe that clindamycin, and preferably oral clindamycin, should be considered as first-line therapy for women with bacterial vaginosis during the second trimester, and metronidazole should either be avoided or combined with erythromycin. It remains unclear whether asymptomatic pregnant women should be screened and treated for bacterial vaginosis. FEBRUARY JOGC FÉVRIER 2007 l 115 LETTER TO THE EDITOR J Obstet Gynaecol Can 2007;29(2):115–116