Hi, Thanks for query, As the result of your urine report doesn t change after taking so may cephalexin doesn t work or developed resistance. Have you any other symptoms of UTI except report shows pus cells only?Some times pregnancy also causes mild infection leads to presence of pus cells in urine. You should go for culture sensitivity report to identify bacteria. Cephalexin has been assigned to pregnancy category B by the FDA. Animal studies have failed to reveal evidence of fetotoxicity or teratogenicity. There are no controlled data in human pregnancy. However, the drug has been used in various stages of pregnancy without evidence of fetal harm. Cephalexin should only be given during pregnancy when need has been clearly established. Thanks.