The prevalence of positive urine dipstick testing and urine culture in the asymptomatic pregnant woman: A cross-sectional study

Objective: Pregnancy induces unique physiological changes to the urinary tract, leaving pregnant women more susceptible to pyelonephritis. Urinary tract infections are generally diagnosed using urine sampling and testing with reagent sticks (dipstick) or laboratory culture. This study aimed to establish the prevalence of positive urine reagent strip and urine culture in asymptomatic pregnant women.

Study design: This was a cross-sectional study of 300 women attending routine antenatal clinics. Samples were analysed using an automated urine dipstick analyser for the presence of glucose, protein, leucocyte esterase, blood, and nitrites. All samples were cultured. Multinomial logistic regression was performed to investigate risk factors for urine contamination and infection. Sensitivities and specificities were calculated for common dipstick findings for positive and mixed urine culture.

Results: One-in-three (37.0 % [111/300], 95 % CI 31.6-42.8 %) women had at least one positive finding on reagent strip testing. Ten per cent ([29/300], 95 % CI 6.7-13.7 %) of samples had a positive culture for a single organism, whereas 46.7 % ([140/300], 95 % CI 40.9-52.5 %) of samples were positive for multiple organisms (mixed culture). 43.7 % ([131/300], 95 % CI 38.0-49.5 %) of samples had a negative culture. Organisms cultured were similar to previous reports from high-income countries. BMI was identified on regression analysis as a risk factor for contamination.

Conclusions: There is a high prevalence of positive urine dipstick and contaminated culture in asymptomatic pregnant women. BMI is a risk factor for urine culture contamination and further research into this topic is essential given trends in obesity worldwide.

Keywords: Asymptomatic bacteriuria; Pregnancy; Urinalysis; Urine dipstick.