PURPOSE: We compared the effects of daily cranberry juice cocktail to those of placebo during pregnancy on asymptomatic bacteriuria and symptomatic urinary tract infections.MATERIALS AND METHODS: A total of 188 women were randomized to cranberry or placebo in 3 treatment arms of A-cranberry 3 times daily (58), B-cranberry at breakfast then placebo at lunch and dinner (67), and C-placebo 3 times daily (63). After 27.7% (52 of 188) of the subjects were enrolled in the study the dosing regimens were changed to twice daily dosing to improve compliance.RESULTS: There were 27 urinary tract infections in 18 subjects in this cohort, with 6 in 4 group A subjects, 10 in 7 group B subjects and 11 in 7 group C subjects (p = 0.71). There was a 57% and 41% reduction in the frequency of asymptomatic bacteriuria and all urinary tract infections, respectively, in the multiple daily dosing group. However, this study was not sufficiently powered at the alpha 0.05 level (CI 0.14-1.39 and 0.22-1.60, respectively, incidence rate ratios). Of 188 subjects 73 (38.8%) withdrew, most for gastrointestinal upset.CONCLUSIONS: These data suggest there may be a protective effect of cranberry ingestion against asymptomatic bacteriuria and symptomatic urinary tract infections in pregnancy. Further studies are planned to evaluate this effect.