Should asymptomatic bacteriuria be treated in pregnant patients in the first trimester?

From the Guidelines

Yes, asymptomatic bacteriuria should be treated in pregnant patients during the first trimester. The recommended treatment typically involves a 3-7 day course of antibiotics such as nitrofurantoin (100mg twice daily), amoxicillin-clavulanate (500mg/125mg twice daily), or cephalexin (500mg four times daily) 1. Treatment is essential because untreated asymptomatic bacteriuria in pregnancy significantly increases the risk of developing pyelonephritis (kidney infection) by 20-30%, which can lead to preterm birth and low birth weight. Additionally, treating asymptomatic bacteriuria reduces the risk of subsequent pyelonephritis by 70-80% 1. After treatment, a follow-up urine culture should be performed to confirm clearance of the infection. Screening for asymptomatic bacteriuria is typically done at the first prenatal visit using urine culture, and any bacterial growth of ≥105 colony-forming units/mL of a single organism warrants treatment, even in the absence of symptoms. The choice of antibiotic should be based on culture sensitivity results and safety profile during pregnancy.

Some key points to consider:

• Asymptomatic bacteriuria is associated with an increased risk of pyelonephritis and low birth weight in pregnant women 1.
• Urine culture is the gold standard for detecting asymptomatic bacteriuria, and a positive test result is defined as the presence of at least 105 colony-forming units per mL of urine, of a single uropathogen, and in a midstream clean-catch specimen 1.
• The USPSTF recommends screening for asymptomatic bacteriuria in pregnant women at 12 to 16 weeks' gestation or at the first prenatal visit, if later, and treating those with positive results 1.
• The optimal frequency of subsequent urine testing during pregnancy is uncertain, and further research is needed to clarify this issue 1.

From the Research

Asymptomatic Bacteriuria in Pregnant Patients

• Asymptomatic bacteriuria occurs in 5% to 10% of pregnancies and, if left untreated, can lead to serious complications 2.
• The prevalence of asymptomatic bacteriuria among pregnant women is reported to be around 7.3% in some studies 3.
• Pregnancy enhances the progression from asymptomatic bacteriuria to symptomatic bacteriuria, which if left untreated, could lead to acute pyelonephritis and other adverse outcomes such as prematurity, postpartum, hypertensive disease, anaemia, UTIs and higher foetal mortality rates 3.

Treatment of Asymptomatic Bacteriuria

• Routine urine culture test should be carried out for all antenatal women, to detect asymptomatic bacteriuria, and every positive case should be treated with appropriate antibiotic therapy, to prevent any obstetric complication which is associated with pregnancy 3.
• Asymptomatic bacteriuria should not be treated except in pregnant women, in patients prior to undergoing an invasive surgical procedure, or renal transplant recipients in the early postrenal transplant period 4.
• It is recommended to obtain a urinalysis during the first trimester in order to detect asymptomatic bacteriuria and treat those cases with positive urine culture 5.

Screening and Diagnosis

• All pregnant women should be screened for asymptomatic bacteriuria, and urinary tract infections should be promptly treated to prevent adverse pregnancy outcome 6.
• A urine culture must be obtained during the first trimester of pregnancy and should be repeated after completion of adequate therapy of an infection, particularly if bacteriuria is detected in the first trimester 5.

Antibiotic Regimens

• Different antibiotic regimens have been compared for treating asymptomatic bacteriuria in pregnancy, but no definitive conclusion can be drawn on the most effective and safest antibiotic regimen 2.
• The choice of antibiotic regimen may depend on factors such as cost, local availability, and side effects 2.