Epidural analgesia often leads to an increase in the number of catheterisations because of the modifications that result in the physiology of the urinary tract. These catheterisations lead to lower urinary tract infections. Our study on 312 patients shows that: under epidural analgesia it is necessary to carry out catheterisation 3.6 times more frequently; urinary tract infections are 2.6 times more frequent under epidural analgesia; the incidence of urinary tract infection multiplies in accordance with the number of catheterisations whether there has been epidural analgesia or not; a single prophylactic dose of 3 g of amoxycillin can avoid three-quarters of these infections.