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Urinary Tract Infections in Pregnancy

Practice Essentials

Pregnancy causes numerous changes in the woman’s body that increase the likelihood of urinary tract infections (UTIs). Hormonal and mechanical changes can promote urinary stasis and vesicoureteral reflux. These changes, along with an already short urethra (approximately 3-4 cm in females) and difficulty with hygiene due to a distended pregnant belly, help make UTIs the most common bacterial infections during pregnancy.

Untreated bacteruria  during pregnancy is associated with risks to both the fetus and the mother, including pyelonephritis, preterm birth, low birth weight, and increased perinatal mortality. In general, pregnant patients are considered immunocompromised UTI hosts because of the physiologic changes associated with pregnancy (see Pathophysiology). These changes increase the risk of serious infectious complications from symptomatic and asymptomatic urinary infections even in healthy pregnant women. (See Urinary Tract Infection in Females.)

Oral antibiotics are the treatment of choice for asymptomatic bacteriuria and cystitis. The standard course of treatment for pyelonephritis is hospital admission and intravenous antibiotics. Antibiotic prophylaxis is indicated in some cases (see Treatment). Patients treated for three or more episodes of cystitis or one episode of pyelonephritis during pregnancy should be continued on daily prophylactic antibiotics for the duration of their pregnancy.

Annual health costs for UTI exceed $1 billion. Although the condition-specific cost of asymptomatic bacteriuria or UTI in pregnancy is unknown, screening for these conditions in pregnant women is cost-effective, compared with treating UTI and pyelonephritis without screening. Goals for future research include targeting low-income groups and women in developing countries for screening and early treatment, as well as determining whether a causal relation exists between maternal UTI and childhood neurologic consequences.

For patient education information, see the following:

Urinary Tract Infection (UTI)

Urinary Tract Infections in Pregnancy

What If I Get a UTI While I’m Pregnant?

Definitions of key terms

Urinary tract infection

UTI is defined as the presence of at least 100,000 organisms per milliliter of urine in an asymptomatic patient, or as more than 100 organisms/mL of urine with accompanying pyuria (> 7 white blood cells [WBCs]/mL) in a symptomatic patient. A diagnosis of UTI should be supported by a positive culture for a uropathogen, particularly in patients with vague symptoms.

Asymptomatic bacteriuria

Asymptomatic bacteriuria is commonly defined as the presence of more than 100,000 organisms/mL in 2 consecutive urine samples in the absence of declared symptoms. Untreated asymptomatic bacteriuria is a risk factor for acute cystitis (40%) and pyelonephritis (25-30%) in pregnancy. This usually occurs in early pregnancy. Risk factors include prior UTIs, pre-existing diabetes, increased parity, and low socioeconomic status. 

Cystitis

Acute cystitis involves only the lower urinary tract; it is characterized by inflammation of the bladder as a result of bacterial or nonbacterial causes (eg, radiation or viral infection). Acute cystitis develops in approximately 1- 2% of pregnant patients, of whom 60% have a negative result on initial screening. Signs and symptoms include hematuria, dysuria, suprapubic discomfort, frequency, urgency, and nocturia. These symptoms are often difficult to distinguish from those due to pregnancy itself.

Acute cystitis is complicated by upper urinary tract disease (ie, pyelonephritis) in 15-50% of cases.

Acute pyelonephritis

Pyelonephritis is the most common urinary tract complication in pregnant women, occurring in approximately 0.5-2% of all pregnancies. Acute pyelonephritis is characterized by fever, flank pain, and tenderness in addition to significant bacteriuria. Other symptoms may include nausea, vomiting, frequency, urgency, and dysuria. Most cases of pyelonephritis occur in the second and third trimester. 

Additional risk factors for complicated UTI in pregnancy include the following
:

Immunosuppression

Pre-existing diabetes

Sickle cell anemia

Neurogenic bladder

Recurrent or persistent UTIs before pregnancy

Tobacco use

Age < 20 years

Late presentation for prenatal care

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