Between 5% and 10% of pregnant women have bacteria in their urine without symptoms of infection (asymptomatic bacteriuria). If left untreated, women may go on to develop serious complications such as kidney infection or preterm birth. In this review we looked at studies comparing different antibiotic treatments for asymptomatic bacteriuria to see which antibiotics or which course of the same antibiotics (shorter versus longer courses) were most effective for reducing infection. We also looked at side effects such as vomiting. The studies included in this review failed to demonstrate any newer antibiotic or regimen which would be better than the older antibiotics and the traditional regimen.
We included five randomized controlled trials involving 1140 women with urine test results showing asymptomatic bacteriuria. Each of the five studies looked at different antibiotics; thus, we have not pooled the results. Four of the comparisons (fosfomycin versus cefuroxime; pivmecillinam versus ampicillin; cephalexin versus Miraxid® (pivmecillinam 200 mg and pivampicillin 250 mg); and cycloserine versus sulphadimidine) showed no definite advantage of one antibiotic over another for treating infection, side effects, or safety. Ampicillin compared with pivmecillinam resulted in less vomiting and was thus better tolerated by the women in one study. There was however no difference in curing present infection and preventing recurring infection in women who took ampicillin compared with those who took pivmecillinam. In another study comparing a one-day versus a seven-day course of nitrofurantoin, the longer course was better in treating bacteria in urine during pregnancy. Women receiving the shorter course had more persistent infection but no clear difference in symptomatic infection at two weeks, nausea or preterm birth.