thesis m-s Faculty of Medicine - Ain Shams University.Obstetrics and Gynaecology

Includes bibliographical references.

Asymptomatic bacteriuria is a major risk factor for the development of urinary tract infection (UTI). During pregnancy, many changes occur in the structure and function of the urinary tract that predispose pregnant women to upper UTI. Although there is a small risk of development of acute episodes of UTI in early pregnancy, there will be a substantial increase risk (from 30% to 60%) during the last trimester.
ASB is defined as a finding of more than 105 CFU/ml of clean catch urine sample in a clinically asymptomatic person.
The prevalence of asymptomatic bacteriuria during pregnancy ranges from about 2 to10%, There are a number of conditions associated with an increased prevalence of asymptomatic bacteriuria in pregnancy including low socioeconomic status, sickle trait, diabetes mellitus and grand multiparity (more than five times) ; each is associated with two-fold increase in the rate of bacteriuria.
A urine culture obtained at 12-16 weeks of pregnancy will identify 80% of women who will ultimately have asymptomatic bacteriuria in pregnancy, with an additional 1-2% identified by repeated monthly screening.
Initial studies reported 20% to 27% of women with asymptomatic bacteriuria developed pyelonephritis compared to 0.4% to 1.2% of those without bacteriuria. A more recent study reported 13% of untreated women with asymptomatic bacteriuria developed pyelonephritis, compared with 0.4% of those with negative screening cultures.
Failure to treat bacteriuria during pregnancy increases the risk of development of complications, such as preterm labour, transient renal failure, sepsis, shock and haematological abnormalities.
The mechanism by which asymptomatic bacteriuria promotes preterm labour is not clear, but subclinical amnionitis or phospholipid A2 production by bacteria have been proposed.
The organisms that cause UTIs during pregnancy are the same as those found in non-pregnant patients. Escherichia coli accounts for 80 to 90 percent of infections. Other gram-negative rods such as Proteus mirabilis and Klebsiella pneumoniae are also common. Gram-positive organisms such as group B streptococcus and Staphylococcus saprophyticus are less common causes of UTI.
The gold standard for detection of bacteriuria is urine culture, but this test is costly and takes 24 to 48hrs to obtain results. The accuracy of faster screening methods (e.g., leukocyte esterase dipstick, nitrite dipstick, urinalysis and urine Gram staining) has been evaluated.
This study includes 321 pregnant women attending the OPC of Ain Shams University Maternity Hospital after comprehensive history taking and complete physical examination, clean catch midstream urine sample had been taken for urine culture, microscopic examination and urine dipstick analysis.
Among the 321 women included in this study, the gold standard urine culture stated that 40 pregnant women have bacteriuria (12.5%), nitrite test have diagnosed 13 cases of them while the remaining 27 cases were nitrite negative, LE test have diagnosed 34 cases while the remaining 6 cases were LE negative, combining the two tests makes no difference, ME have diagnosed 23 cases while 17 cases were microscopically negative.
Among this study there were 281 pregnant women who have non bacteriuric samples using urine culture, 260 of them were nitrite negative. This means that nitrite test is a quite good negative test, while 180 were LE negative and 175 were microscopically negative.
In conclusion, urine dipstick tests and microscopic urine analysis have been evaluated in this study, dipstick test is more accurate than urine microscopy, but their low sensitivity, high false negative results and their poor NPV make them unreliable. Therefore, urine culture remains the most reliable tool for screening of UTI.

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