Optimal timing to screen for asymptomatic bacteriuria during pregnancy: first vs. second trimester

Objectives: Although current guidelines advice to screen for asymptomatic bacteriuria during pregnancy, little is known about the best moment of testing. The goal of this study is to analyze the optimal timing (first vs. second trimester) to screen for asymptomatic bacteriuria during pregnancy.

Methods: A retrospective cohort analysis, comparing patients that were screened for asymptomatic bacteriuria in the first vs. second trimester was performed. The main question was to compare the rate of positive urinary culture in both trimesters. Study included patients all followed a prenatal consultation at the University Hospital of Brussels between 2012 and 2017. Other outcomes considered were the nature of identified germs, treatments, possible risk and confounding factors (age, BMI, gravidity-parity-abortus [GPA], type of conception, ethnicity, education, prior urinary tract infection (UTI), diabetes, hypertension, prior preterm delivery and sickle cell disease) and complications (UTI, preterm delivery, preterm rupture of the membranes and chorio-amnionitis).

Results: A total of 2,005 consecutive files were reviewed, 655 concerned patients screened during the first trimester group and 1,350 in the second trimester group. Asymptomatic bacteriuria was present in only 71 cases (3.54%), 23 in the first trimester group (3.50%) and 48 in the second trimester group (3.55%). Escherichia coli was the most frequently identified germ (37 cases (1.8%), 14 in the first trimester group and 23 in the second trimester group). Our logistic regression analysis shows no statistical difference according to the moment the urinary culture was done for the presence of asymptomatic bacteriuria (E. coli or others), for its association with hospitalization for pyelonephritis, preterm contractions, preterm pre-labor rupture of the membranes (PPROM) and/or preterm delivery.

Conclusions: If recommendations remain to screen for asymptomatic bacteriuria at least once during pregnancy, this study indicates that the moment of testing (first vs. second trimester) has no clinical impact on obstetrical outcomes.