Objective: The purpose of this study was to compare the following outcome variables in pregnant patients with sickle cell trait and matched pregnant control patients: asymptomatic bacteriuria,acute cystitis, urinary pathogens that were present, and pyelonephritis. Study design: This was a retrospective cohort study that was conducted at a university clinic. Pregnant patients with sickle cell trait (n = 455) were matched with control patients (n = 448) for race, age, gestational age at entry into prenatal care, and number of prenatal visits. Results: Women with sickle cell trait received urine testing significantly more often. There was no difference in the incidence of positive urine cultures, urinary pathogens, or asymptomatic bacteriuria among the comparison groups. Sickle cell trait carriers had significantly higher rates of pyelonephritis, but many affected patients had risk factors, such as previous pyelonephritis or noncompliance with therapy. Conclusion: Sickle cell trait carriers were no more susceptible to acute cystitis and asymptomatic bacteriuria than were the control patients. On the basis of these data, we outline recommendations for urinary screening and pyelonephritis prevention in pregnant patients with sickle celltrait. Objective: The purpose of this study was to compare the following outcome variables in pregnant patients with sickle cell trait and matched pregnant control patients: asymptomatic bacteriuria, acute cystitis, urinary pathogens that were present, and pyelonephritis. Study design: This was a retrospective cohort Pregnant patients with sickle cell trait (n = 455) were matched with control patients (n = 448) for race, age, gestational age at entry into prenatal care, and number of prenatal visits. : Women with sickle cell trait received urine testing significantly more often. There was no difference in the incidence of positive urine cultures, urinary pathogens, or asymptomatic bacteriuria among the comparison groups. Sickle cell trait carriers had significantly higher rates of pyelonephritis, but many affected patients had risk factors, such as previous pyelonephritis or noncompliance with therapy. Conclusion: Sickle cell trait carrie rs were no more susceptible to acute cystitis and asymptomatic bacteriuria than were the control patients. On the basis of these data, we outline recommendations for urinary screening and pyelonephritis prevention in pregnant patients with sickle celltrait.