REVIEW ARTICLE
URINARY TRACT INFECTIONS IN PREGNANCY
Acute cystitis relates to infection of the urinary bladder. Very often the urethra is also infected. The major distinguishing feature of acute cystitis from asymptomatic bacteriuria is the presence of dysuria, urgency and frequency. Usually the patient remains afebrile. Severe systemic symptoms such as nausea, vomiting, high grade fever and distress are usually absent. Most mothers may not be aware that they are having the infection because urgency and frequency are common symptoms in a normal pregnancy.
Acute pyelonephritis is infection of the kidney and the pelvic ureter. It is a serious systemic illness affecting 1-2% of all pregnancies and the most common non-obstetric cause of hospital admission during pregnancy.3 This complication is characterised by high-grade fever, chills and rigors, headache, nausea, vomiting, lumbar pain and in serious cases, reduced urine output. Without treatment it can cause preterm labour and maternal septicaemia. Recurrent pyelonephritis has been implicated as a cause of intra uterine growth restriction and foetal death. The overall incidence of recurrence is about 2-3% and it can recur during the same pregnancy.3
AETIOLOGICAL AGENTS
Escherichia coli (E. coli) is the major aetiological agent in causing UTI, which accounts for up to 90% of cases.1 Proteus mirabilis and Klebsiella pneumoniae are less frequent offenders. Less commonly, enterococci including Gardnerella vaginalis and Ureaplasma ureolyticum are known agents in UTI. Gram-positive organisms are even less common in which Group B streptococcus, Staphylococcus saprophyticus and Staphylococcus haemolyticus are recognised organisms.1,5
SCREENING
Due to the high prevalence of asymptomatic bacteriuria in pregnancy and its serious consequences, it is justifiable to screen for this condition in pregnancy. Various methods are used to screen for asymptomatic bacteriuria; among these are urinalysis to look for protein, white blood cells, red blood cells, urine dipstick for nitrites and leukocyte esterase. Although these tests are easily available and rapid, they have relatively poor predictive values and false negatives results are common.1,8 The gold standard for detecting bacteriuria in pregnancy is urine culture. The limiting factor is the relative high cost and delay in results (it takes 24 to 48 hours to culture the organism). Therefore it is recommended that physicians will have to balance between the cost and effectiveness of the screening test before deciding on it.
TREATMENT
Asymptomatic bacteriuria should be treated with antimicrobials even though the mother has no clinical symptoms. Various studies have proven that early treatment of asymptomatic bacteriuria in pregnancy reduces the incidence of acute pyelonephritis and decreases the incidence of pre-term delivery and low birth weight infants.1,2,8 Early recognition and treatment of asymptomatic bacteriuria can reduce up to 70% of acute symptomatic UTI.3
The antibiotic of choice should be safe for both mother and baby (Table 2). Amoxycillin is a safe choice but in recent years E. coli has become increasingly resistant to amoxycillin. Alternative drugs are now used as first line treatment. Cephalosporins and nitrofurantoin are safe for pregnant mothers; as both have high urinary concentration and are effective against E. coli. There is insufficient data to recommend any specific type of treatment regime in symptomatic UTI in pregnancy. Common antibiotics such as nitrofurantoin and cefuroxime are effective and complications are rare.4 Nitrofurantoin has the advantage of sparing the disruption of normal vaginal flora but should be avoided at third trimester because a potential risk of haemolysis if the foetus is G6PD-deficient.5 Sulphonamides can be used in first and second trimester but it is best avoided in third trimester because it competes for bilirubin-binding sites on albumin in the foetus and causes severe jaundice and kernicterus especially in pre-term babies.1,3 Quinolones and tetracyclines have possible toxic effects on the foetus and these medications are contraindicated in pregnancy.1,5,6 A 7 to 10-day course of oral antibiotic treatment is usually adequate in a majority of the cases of asymptomatic bacteriuria and acute cystitis.1,3 Patients should be advised to come for a repeat urine culture 1-2 weeks after completing antibiotics. Mothers who are treated for shorter period of time are more likely to have higher recurrence rate and this may lead to serious consequences.
