Pregnancy is a predisposing factor for urinary tract infection and pregnant women suffering from this pathology are exposed to dangerous risks which may condition maternal wellbeing and fetal prognosis. The apparently paradoxal finding of a higher incidence of perinatal problems in pregnant women with asymptomatic bacteriuria compared to those with manifest infections may be explained by the fact that the latter are adequately treated, whereas asymptomatic bacteriuria, which is difficult to diagnose, may continue in a subtle form for the entire duration of pregnancy. This emphasises the importance of the early diagnosis of infection using a protocol based on urine tests and urine culture and the adequate treatment of all cases of asymptomatic bacteriuria in order to reduce the incidence of maternal and fetal complications (acute pyelonephritis, increased fetal morbidity and mortality). The choice of the antibiotic to be used must be made on the basis of the urine culture test, the stage of gestation, maternal clinical data and the characteristics of the antibiotic itself (pharmacokinetics, maternal and fetal toxicity). With regard to the treatment protocol, the "single-dose" protocol is currently preferred. After negative urine culture tests, all patients must carry out a complete urine test each month with hormonal and echographic monitoring of the fetoplacental unit.