Introduction

Urinary tract infection (UTI) is more common during pregnancy because the hormonal and mechanical changes in the urinary tract make women more vulnerable starting from 6 weeks through 24 weeks.

Urinary tract infection in pregnancy involves

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  Urethra

  
  
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  Bladder

  
  
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  Ureter

  
  
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  Kidneys

Most of the infections are limited to the bladder and urethra but can lead to kidney infection.

Predisposing Pregnancy Factors

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  Women are eight times more likely to get urinary tract infections, due to proximity of the genital tract and the rectum where E. coli are found in faecal matter.

  
  
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  Progesterone hormonal changes promote urinary stasis and vesicoureteral reflux. Progesterone may also induce smooth muscle relaxation in the ureter.

  
  
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  Short urethra and difficulty with hygiene due to a distended pregnant abdomen makes women more prone to have UTIs.

  
  
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  Physiological and structural changes in the urinary tract organs.

  
  
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  Compression from uterine enlargement and relative dextrorotation.

  
  
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  Compression from the right ovarian venous plexus that crosses over the ureter, and finally bladder pressure and capacity are also altered due to decreased tone.¹

  
  
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  In addition, the immunosuppression of pregnancy may contribute as mucosal interleukin-6 levels and serum antibody responses to E. coli antigens appear to be lower in pregnant women.²

  
  
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  Easier contamination because of the proximity of the anal orifice to the urethra.

  
  
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  UTIs are associated with risks to both the fetus and the mother, including pyelonephritis, preterm birth, low birthweight and increased perinatal mortality.

Signs and Symptoms

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  Pain or burning (dysuria), frequency, urgency, nocturia

  
  
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  Blood or mucus in the urine

  
  
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  Cramps or pain in the lower abdomen

  
  
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  Pain during sexual intercourse

  
  
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  Chills, fever, sweats, leaking of urine (incontinence)

  
  
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  Change in amount of urine, cloudy, smells foul or unusually strong

  
  
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  Pain, pressure or tenderness in the suprapubic area of the bladder

Asymptomatic Bacteriuria

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  Asymptomatic bacteriuria is the presence of more than 100 000 organisms/mL in two consecutive urine samples in the absence of declared symptoms.

  
  
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  Untreated, it is a risk factor for acute cystitis (40 per cent) and pyelonephritis (25–30 per cent) in pregnancy.³

  
  
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  The United States Preventive Services Task Force as well as several other international medical societies recommend screening for and treatment of asymptomatic bacteriuria. Screening and treatment of asymptomatic bacteriuria is cost-effective, especially in populations where its incidence is greater than 2 per cent. If untreated, up to 30 per cent of cases will progress to pyelonephritis.

  
  
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  With proper treatment of asymptomatic bacteriuria, the number needed to treat to prevent one episode of pyelonephritis is only seven, and the rate of hospitalisation for pyelonephritis is reduced to 1.4 per cent.

  
  
  
  
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    A review of randomised trials comparing antibiotic treatment versus no antibiotic treatment of asymptomatic bacteriuria resulted in a greater decrease in both pyelonephritis and low-birthweight babies. The rates of preterm delivery, however, were not affected by treatment. [EL 1]

    
    
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    In a meta-analysis of 19 studies, among women without bacteriuria, the risks of preterm birth and a low-birthweight infant were one-half and two-thirds respectively the risks among women with asymptomatic bacteriuria.⁴ [EL 1]

    
    
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    Other pregnancy complications have also been associated with bacteriuria. A case control study of over 15 000 pregnant women found an increased risk of pre-eclampsia with either asymptomatic bacteriuria or symptomatic UTI.⁵ [EL 2]

  
  

Asymptomatic bacteriuria during pregnancy increases the risk of pyelonephritis and has been associated with adverse pregnancy outcomes, therefore antibiotic therapy should be given according to the culture and sensitivity.

Acute Cystitis

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  Involves only the lower urinary tract

  
  
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  Is characterised by inflammation of the bladder

  
  
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  Affects approximately 1 per cent of pregnant patients

  
  
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  Signs and symptoms include haematuria, dysuria, suprapubic discomfort, frequency, urgency and nocturia

  
  
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  Acute cystitis is complicated by upper urinary tract disease (i.e. pyelonephritis) in 15–50 per cent of cases⁶ Acute cystitis occurs in 1–2 per cent of pregnancies⁷

Symptoms of Acute Cystitis

Urinary frequency, dysuria and urgency; however no correlation has been clearly established between acute cystitis of pregnancy and increased risk of low birthweight, preterm delivery or pyelonephritis, perhaps because pregnant women with symptomatic lower UTI usually receive treatment, contrary to asymptomatic bacteriuria where it may pass unnoticed as it is an asymptomatic condition.

Treatment of cystitis is the same as that for asymptomatic bacteriuria.

A Cochrane review of nine studies showed that no single treatment regimen for cystitis in pregnancy was superior to another. If symptoms persist with negative urine cultures, consideration of other diagnoses, including cervicitis, vaginitis and especially urethritis, should be considered and other cultures taken appropriately.

Acute Pyelonephritis

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  Is the most common urinary tract complication in pregnant women, occurring in approximately 2 per cent of all pregnancies

  
  
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  Is characterised by fever, flank pain and tenderness in addition to significant bacteriuria

  
  
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  Other symptoms may include nausea, vomiting, frequency, urgency and dysuria

  
  
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  Women with additional risk factors (e.g. immunosuppression, diabetes, sickle cell anaemia, neurogenic bladder, recurrent or persistent UTIs before pregnancy) are at an increased risk for a complicated UTI⁸

Pyelonephritis also complicates 1–2 per cent of pregnancies.⁹

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  Symptoms and signs of pyelonephritis include symptoms of cystitis, chills, flank pain, nausea, vomiting, fever and costovertebral angle tenderness.

  
  
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  The diagnosis is made by urine culture. One to two bacteria per high-power field (hpf) on an unspun urine sample or greater than 20 bacteria per hpf on a spun urine sample correlates with 100 000 cfu/mL. The presence of white blood cell casts on urinalysis can confirm the diagnosis as well.

  
  
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  Bacteraemia is present in 10–20 per cent of patients with pyelonephritis. Standard treatment is administration of intravenous (IV) antibiotics until the patient remains afebrile for at least 48 hours.

  
  
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  If bacteraemia is present, IV treatment should be extended to a period of at least five to seven days. As with cystitis, E. coli is cultured in 70–81 per cent of cases.

  
  
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  More serious complications of pyelonephritis include septic shock and pulmonary insufficiency in 10 per cent of cases.

  
  
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  Furthermore, suppressive antibiotic therapy is recommended for the remainder of the gestation, with a common choice being nitrofurantoin 100 mg orally, at bedtime.

  
  
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  In non-compliant patients, monthly urine cultures should be obtained to screen for recurrent bacterial growth.

Recurrent Pyelonephritis

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  Recurrence rate is approximately 20 per cent.

  
  
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  Most cases of pyelonephritis occur during the second and third trimesters but can occur in the postpartum period as well.¹⁰

  
  

  As a result, low-dose antimicrobial suppressive therapy with an agent to which the original organism is susceptible is warranted for the remainder of the pregnancy; reasonable options include nitrofurantoin (50–100 mg orally at bedtime) or cephalexin (250–500 mg orally at bedtime).

  
  
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  Monthly cultures are not necessary if preventive therapy is administered; however, at least one culture, later, at the start of the third trimester, to ensure preventive therapy is working should be done.

Obstetric management: pyelonephritis is not itself an indication for delivery. If induction of labour or caesarean delivery is required for obstetrical indications, it is advisable to wait until the patient is afebrile, as long as delaying the delivery is relatively safe for the mother and fetus.

Tocolysis should not be used when pyelonephritis triggers preterm labour. Risk of pulmonary oedema and acute respiratory distress syndrome (ARDS) may be exacerbated by administration of tocolysis with or without corticosteroids.