A Cochrane review included 8 studies 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 (RR 0.88, 95% CI 0.72 to 1.09; 6 trials, n=3663). 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 but 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). There was reduction in the risk of postpartum endometritis (RR 0.55, 95% CI 0.33 to 0.92; 1 study, n=196) in all risk pregnant women (with/without previous preterm birth and had BV during the current pregnancy). Regarding the route of antibiotic administration, vaginal antibiotic prophylaxis during pregnancy did not prevent infectious pregnancy outcomes.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment in one third of the studies and selective reporting).