Antibiotics for Treating Bacterial Vaginosis in Pregnancy in Women with Previous Preterm Birth

Summary

A multicentre, double-blind RCT 3 assessed whether treatment of bacterial vaginosis decreases late miscarriages or spontaneous very preterm birth. 84 530 pregnant women before 14 weeks' gestation were screened. 5630 had BV, of whom 3105 were randomly assigned to groups in the low-risk trial (n=943 to receive single-course clindamycin, n=968 to receive triple-course clindamycin, and n=958 to receive placebo) or high-risk subtrial (n=122 to receive single-course clindamycin and n=114 to receive triple-course clindamycin). In 2869 low-risk pregnancies, the primary outcome occurred in 22 (1.2%) of 1904 participants receiving clindamycin and 10 (1.0%) of 956 participants receiving placebo (RR 1.10, 95% CI 0.53 to 2.32; p=0.82). In 236 high-risk pregnancies, the primary outcome occurred in 5 (4.4%) participants in the triple-course clindamycin group and 8 (6.0%) participants in the single-course clindamycin group (RR 0.67, 95% CI 0.23 to 2.00; p=0.47). The most commonly reported adverse event was diarrhoea in the clindamycin groups. No severe adverse event was reported in any group. Adverse fetal and neonatal outcomes did not differ significantly between groups in the high-risk subtrial.

A Cochrane review [Abstract] 1 included 21 good quality studies with a total of 7 847 women with bacterial vaginosis or intermediate vaginal flora (treatment with oral metronidazole: 5 trials; oral metronidazole plus erythromycin, oral clindamycin, ampicillin, vaginal metronidazole gel, 1 trial each; intravaginal clindamycin alone: 6 trials). Ten trials performed microbiological follow up and 7 trials gave a second course of treatment (four only if bacterial vaginosis was not eradicated). Antibiotic therapy was effective at eradicating bacterial vaginosis during pregnancy (RR 0.42; 95% CI 0.31 to 0.56; 10 trials, n=4403, I² = 91%), and reduced the risk of late miscarriage (RR 0.20; 95% CI 0.05 to 0.76; 2 trials, n=1270, I² = 0%). Treatment did not reduce the risk of preterm birth (PTB) before 37 weeks (RR 0.88; 95% CI 0.71 to 1.09; 13 trials, n=6491, I² = 48%), or the risk of preterm prelabour rupture of membranes (PPROM) (OR 0.88, 95% CI 0.61 to 1.28; four trials, 2579 women). However, treatment before 20 weeks' gestation reduced the risk of preterm birth less than 37 weeks (OR 0.63, 95% CI 0.48 to 0.84; 5 trials, 2387 women). In women with a previous PTB, treatment did not affect the risk of subsequent PTB (OR 0.83, 95% CI 0.59 to 1.17, 5 trials, 622 women); however, it decreased the risk of PPROM (OR 0.14, 95% CI 0.05 to 0.38) and low birthweight (OR 0.31, 95% CI 0.13 to 0.75; 2 trials, 114 women). In women with abnormal vaginal flora (intermediate flora or bacterial vaginosis) treatment reduced the risk of PTB before 37 weeks (Peto OR 0.51, 95% CI 0.32 to 0.81; 2 trials, 894 women). Clindamycin did not reduce the risk of PTB before 37 weeks (Peto OR 0.80, 95% CI 0.60 to 1.05; 6 trials, 2406 women).

Another Cochrane review [Abstract] 2included 8 trials with a total of 4 300 subjects. The study aimed to detect the effect of prophylactic antibiotic administration in the second or third trimester on pregnancy outcomes. Antibiotic prophylaxis in unselected pregnant women did not reduce the risk of prelabour rupture of membranes. There was a risk reduction in preterm delivery (OR 0.64, 95% CI 0.47 to 0.88; 1 study, n=258) in pregnant women with a previous preterm birth and with bacterial vaginosis (BV) during the current pregnancy. There was no risk reduction in pregnant women with previous preterm birth without BV during pregnancy (OR 1.08, 95% CI 0.66 to 1.77; 2 studies, n=500).