Urinary tract infection (UTI) occurs more frequently during pregnancy (reported in 18% of pregnancies [1]). The increased incidence is due to urinary stasis, which results from hormone-mediated ureteral dilation and hypoperistalsis, and pressure of the expanding uterus against the ureters.
Asymptomatic bacteriuria sometimes progresses to symptomatic cystitis or pyelonephritis, although symptomatic UTI is not always preceded by asymptomatic bacteriuria. Pyelonephritis can quickly progress to a systemic infection during pregnancy, resulting in sepsis, disseminated intravascular coagulation, and acute respiratory distress syndrome.
Asymptomatic bacteriuria, UTI, and pyelonephritis increase risk of (2):
Low birth weight
References
1. Johnson CY, Rocheleau CM, Howley MM, Chiu SK, Arnold KE, Ailes EC: Characteristics of Women with Urinary Tract Infection in Pregnancy. J Womens Health (Larchmt). 2021;30(11):1556-1564. doi:10.1089/jwh.2020.8946
2. Romero R, Oyarzun E, Mazor M, Sirtori M, Hobbins JC, Bracken M: Meta-analysis of the relationship between asymptomatic bacteriuria and preterm delivery/low birth weight. Obstet Gynecol. 1989;73(4):576-582. PMID: 2927852
Symptoms and Signs of UTI in Pregnancy
The symptoms of cystitis are the same in pregnant and nonpregnant patients—urinary frequency, urinary urgency, and/or dysuria, and sometimes nocturia. However, some of these symptoms occur during pregnancy without a UTI. Thus, diagnostic tests should be done before treatment.
Acute pyelonephritis occurs more frequently in the second or third trimesters. Symptoms are the same in pregnant and nonpregnant patients and usually include cystitis symptoms combined with upper urinary tract or systemic symptoms (chills, fever, flank pain, colicky abdominal pain, nausea, and vomiting). In pregnant patients, the index of suspicion for pyelonephritis should be high, and a urine test should be done even if some of the characteristic signs and symptoms are not present.
In pyelonephritis, on physical examination, costovertebral angle percussion tenderness is generally present on the infected side.
Diagnosis of UTI in Pregnancy
Urine dipstick test
Urinalysis and culture
As part of routine prenatal care, all pregnant patients should be screened for asymptomatic bacteriuria at an early prenatal visit. Testing for asymptomatic bacteriuria should be done with a urine culture.
Diagnosis of symptomatic UTI is the same in pregnant and nonpregnant patients. A dipstick test of the urine is usually done first, and a urinalysis and culture are sent to the laboratory.
Treatment of UTI in Pregnancy
Antibiotics
For Group B streptococcus, antibiotics during delivery
Treatment of UTI is not changed by pregnancy, with the exception that medications that may harm the fetus (eg, fluoroquinolones) are avoided (1) (see table Safety of Selected Drugs in Pregnancy).
Antibiotic selection is based on urine culture results, local susceptibility, and resistance patterns.
Because asymptomatic bacteriuria may lead to pyelonephritis, any pregnant patient with a positive urine culture should be treated with antibiotics similar to an acute UTI.
Oral antibiotics are given for asymptomatic bacteriuria or acute cystitis. In a symptomatic patient, if a urine dipstick test is positive, empiric treatment should be started immediately and then adjusted, if needed, based on urine culture results.
is contraindicated in pregnant patients at term, during labor and delivery, or when the onset of labor is imminent because hemolytic anemia in the neonate is possible. Pregnant women with G6PD (glucose-6-phosphate dehydrogenase) deficiency should not take nitrofurantoin. Incidence of neonatal jaundice is increased when pregnant women take nitrofurantoin during the last 30 days of pregnancy.
(TMP/SMX) can cause congenital malformations (eg, neural tube defects) and kernicterus
After treatment, some clinicians do a test-of-cure culture. Following a single episode of cystitis or asymptomatic bacteriuria, repeat screening in asymptomatic patients is not required.
Because of the risk of severe infection, pregnant patients with pyelonephritis
Women who have pyelonephritis or have had more than one UTI may require suppressive therapy,
After treatment of pyelonephritis, urine should be cultured monthly.
Patients with any colony count of Group B streptococcus (GBS) in a urine culture at any time during pregnancy (which suggests heavy vaginal–rectal colonization) should be given antibiotic prophylaxis at the time of delivery (2).
Treatment references
1. American College of Obstetricians and Gynecologists (ACOG) Committee on Clinical Consensus—Obstetrics: Urinary Tract Infections in Pregnant Individuals Obstet Gynecol. 2023;142(2):435-445. doi:10.1097/AOG.0000000000005269
2. ACOG: Prevention of Group B Streptococcal Early-Onset Disease in Newborns: ACOG Committee Opinion, Number 797 [published correction appears in Obstet Gynecol. 2020 Apr;135(4):978-979]. Obstet Gynecol. 2020;135(2):e51-e72. doi:10.1097/AOG.0000000000003668
Key Points
Asymptomatic bacteriuria, cystitis, and pyelonephritis increase risk of preterm labor and low birth weight.
Pyelonephritis may result in maternal sepsis, disseminated intravascular coagulation, and acute respiratory distress syndrome.
Screen all pregnant patients for asymptomatic bacteriuria with a urine culture in early pregnancy.
For patients with GBS in a urine culture (any colony count) at any time during pregnancy, treat with prophylactic antibiotics during delivery.
