Bacteriuria in pregnancy with or without clinical symptoms is frequent and increases the risk of pyelonephritis, preterm labour, and low birth weight infants. Commonly used antibiotics such as ampicillin (pivampicillin), amoxicillin, trimethoprim, and sulphonamide are currently associated with a high degree of resistance of the most common pathogen in the urinary tract, Escherichia coli. During the past few decades a number of new and efficient antibacterial antibiotics have been developed. The presumption that a specific drug is safe for both the pregnant woman and the foetus depends on how widely the drug has been used. A recent survey among general practitioners and obstetricians in Denmark, Finland, Norway, and Sweden confirmed that the beta-lactam antibiotic pivmecillinam and nitrofurantoin are the most commonly used agents in the treatment of bacteriuria in pregnancy in the Nordic countries. However, a surprisingly high number of physicians reported that they prescribe sulphonamides during the first two trimesters in spite of resistance of E. coli and possible adverse effects on the foetus.