Urinary tract infections (UTIs) are generally caused by the same pathogens in both pregnant and non-pregnant patients. Escherichia coli remains the most common pathogen but other bacteria such as Klebsiella pneumoniae, Staphylococcus, Streptococcus, Proteus, and Enterococcus may be present. Pyelonephritis is a serious consequence of UTIs, especially for pregnant patients, so it is necessary to ensure prompt evaluation and treatment. Antibiotic selection is ideally tailored to culture sensitivities. Commonly used antibiotics include amoxicillin, ampicillin, cephalosporins, nitrofurantoin, and trimethoprim-sulfamethoxazole. [1] However, some data suggest sulfa derivatives and nitrofurantoin causes congenital disabilities that have led to decreased use in the first trimester. [2] In the late third trimester, trimethoprim-sulfamethoxazole should be avoided due to the potential risk for the development of kernicterus in the infant following delivery. Fluoroquinolones are not recommended as a first-line treatment in pregnancy due to conflicting studies regarding teratogenicity. Short courses are unlikely to be harmful to the fetus, so they are utilized for resistant or recurrent infections. [1]
The 2021 European Association of Urology has the most recently updated guidelines regarding antimicrobial selection for urinary tract infections (UTI) during pregnancy. They recommend short courses of antimicrobial therapy for treatment of cystitis in pregnancy with the following agents: penicillins, cephalosporins, fosfomycin, nitrofurantoin (not in case of glucose-6-phosphate dehydrogenase deficiency and during the end of pregnancy), trimethoprim (not in the first trimester) and sulfonamide (not in the last trimester). [3]
American College of Obstetricians and Gynecologists (ACOG) has withdrawn several committee opinions regarding UTIs in pregnant and non-pregnant women as well as the risk of birth defects for sulfonamides and nitrofurantoin. They provided no rationale for the withdrawal and currently offer no clinical guidance for UTIs. [4], [5], [6] Other guidance such as from the American Academy of Family Physicians (AAFP) or Infectious Diseases Society of America (IDSA) have not been consistently updated or do not apply to pregnancy. [7], [8]
A 2015 Cochrane review assessed the duration of treatment for asymptomatic bacteriuria during pregnancy. Their findings suggest single-dose regimens may be less effective than short (4-7 day) courses, but this recommendation is limited by small sample size, heterogeneous population, and inconsistencies in reported outcomes and trial design. There was no assessment of efficacy or safety for specific antibiotic regimens. [9]
A 2019 meta-analysis assessed the safety of macrolides during pregnancy (N= 21 studies). The analysis showed the increase in the odds of birth defects among women who consumed macrolides during their pregnancy is very low (odds ratio [OR] 1.06, 95% confidence interval [CI] 1.01 to 1.10). A subgroup analysis revealed the association is strongest during the first trimester (OR 1.06, 95% CI 1.01–1.11). Like many teratogen studies, this analysis is limited due to small occurrences and lack of complete information in registries. [10]
A 2020 meta-analysis assessed the association of sulfonamide use during pregnancy and adverse outcomes (N= 10 studies; N= 1,096,350 participants). Maternal exposure to sulfonamides was found to be possibly associated with increased risk of congenital malformations (OR = 1.21, 95% CI 1.07–1.37). The researchers concluded use of sulfonamides in the first trimester of pregnancy and during the entire pregnancy might be associated with congenital malformations. As with many studies examining drug exposure and pregnancy outcomes, it is difficult to assess duration of exposure and prescribing rationale using registry data. [11]