A STUDY OF THE CORRELATION BETWEEN ASYMPTOMATIC BACTERIURIA AND PRETERM LABOR
Mostafa Mahmoud Mahmoud Ibrahim;
Abstract
Preterm delivery refers to birth between the onset of viability and 37 completed week’s gestation. Preterm labor is usually defined as regular contractions accompanied by cervical changes occurring at less than 37 weeks' gestation.
In about half the cases, the cause of preterm delivery is not known. However, accumulating evidence suggests that subclinical intrauterine infection with unknown etiology maybe responsible for the majority of cases.
Preterm infants are at risk for specific diseases such as respiratory distress syndrome, intraventricular hemorrhage, bronchopulmonary dysplasia, patent ductus arteriosus, necrotizing entericolitis, sepsis, apnea and retinopathy.
Preterm birth is the ultimate result of several different pathways that culminate in the initiation of labor before 37 weeks' gestation. It is useful to place preterm births in two broad categories- those that are obstetrically indicated and those that are spontaneous.
The pathogenesis of preterm labor is not well understood, and it is often not clear whether preterm labor represents early idiopathic activation of the normal labor process or results from a pathologic mechanism. So, preterm labor probably represents a syndrome rather than a specific diagnosis, since the causes are varied.
American College of Obstetricians and Gynecologists (1999) reported that the studies of the epidemiology and pathophysiology of preterm birth have identified four pathways leading to preterm labor and delivery:
1. Inflammation.
2. Decidual hemorrhage.
3. Uterine over-distention.
4. Premature activation of the normal physiologic initiators of labor.
The etiology of spontaneous preterm labor and preterm birth is multifactorial but there is overwhelming evidence that infection is an important cause, probably accounting for up to 30% of cases .There is accumulating evidence to support this: Pro inflammatory cytokines such as interleukin 1, 6 & 8 and tumor necrosis factor alpha are found significantly increased concentrations in the amniotic fluid of women in spontaneous preterm labor with infection compared to women without infection. The presence of these cytokines in amniotic fluid and fetal blood has been shown to be associated with fetal and neonatal tissue damage.
Controversy exists regarding the association between asymptomatic bacteriuria during pregnancy and adverse perinatal outcome, including preterm deliveries and low birthweight. Urinary tract infections are the most common medical complication of pregnancy. Asymptomatic bacteriuria is the most prevalent of these infections and it is defined as, the finding of greater than (100,000) colony forming units per mL of clean catch urine specimens or one catheterization specimen. Lower colony counts in asymptomatic women usually represent contamination.
Some physiological changes occurring during the pregnancy expedite the emergence of urinary infections and cause a higher incidence. As a result of hormonal changes, tonus of urinary bladder and ureter is reduced, and subsequently dilatation in the ureter and renal pelvis, incidence of urinary stasis and vesicourteric reflux increase. Increased plasma volume and glomerular filtration rate result in reduction in the urinary concentration. Furthermore, there is an increase in the incidence of glycosuria and aminoaciduria and a reduction in the resistance of urinary tract system against bacteria in pregnancy. Depending on all these developments, the incidence of symptomatic urinary tract infections is increased in pregnancy.
Early in pregnancy there is little impact of hormonal changes on the genitourinary tract and treatment considerations would likely be similar to those for uncomplicated UTI. Hormonal effects later in pregnancy lead to decreased autonomic muscle tone and stasis in the genitourinary tract. There is also an increased risk of reflux and obstruction with pressure of the fetal head at the pelvic brim. These physiological changes suggest management of infection later in pregnancy would be similar to complicated urinary infection. An additional consideration is that antimicrobial selection must consider the potential impact on the fetus.
The prevalence of asymptomatic bacteriuria during pregnancy ranges from about 2 to 12%. While rates from most recent observational studies done in developing countries fall within this range, the prevalence of asymptomatic bacteriuria was reported to be as high as 86.6% in a study from Nigeria, although S. aureus, which is not typically recognized as a uropathogens, made up over a third of the isolates.
Pregnant females with bacteriuria are at high risk of suffering recurrent bacteriuria; this, if left untreated, can cause pyelonephritis late in the pregnancy or puerperium. In the preantibiotic era, pregnant women with bacterial pyelonephritis had a high rate of infant prematurity and perinatal mortality.
In the Cochrane Review of antibiotic treatment for asymptomatic bacteriuria in pregnancy that included ten randomized controlled clinical trials where the outcome of preterm delivery or low birth-weight was reported, antibiotic treatment was shown to be associated with a reduction in this outcome. The mechanism for an association between preterm labor and asymptomatic bacteriuria has not been established, but a theoretical argument is made for a causative role for the production of phospholipase A2 by microorganisms, which then can initiate labor through the activation of prostaglandin. While this mechanism has been well defined for intra-amniotic infection and symptomatic pyelonephritis, there has been no recent research to explore the mechanisms through which asymptomatic bacteriuria exerts adverse pregnancy outcomes. Treatment of asymptomatic bacteriuria identified early in pregnancy decreases the risk of pyelonephritis later in pregnancy by at least 75%. Treatment of asymptomatic bacteriuria also significantly improves the adverse fetal outcomes of premature labor and low birth weight.
This study is a case control study conducted in Ain Shams University Maternity Hospital to investigate the association between asymptomatic bacteriuria and preterm labor. A total of third trimesteric 150 pregnant women were included in this study during the period from February 2012 till March 2013, they were divided into two groups, cases and Control group each 75 patients.
After comprehensive history taking and complete physical examination, clean catch midstream urine sample had been taken for urine culture and sensitivity.
Among the 150 women included in this study, 18 women had true culture bacteriuria giving a prevalence of 12%.
In our study, table 13 showed that prevalence of ASB among cases of preterm labor was 17.6% and among control was 6.7%.There is a statistical significant difference between cases and controls regarding ASB.
The microbiology of bacteriuria in this study (table 14) showed that E.coli was the most common pathogen (67% of the positive cultures) followed by staph aureus and proteus mirabilis. The antibiotic sensitivity patterns were showed in table 14, showing that most of the bacterial isolates were sensitive to nitrofurantoin 61% and cefoperazone 38.8%.
Prevalence of ASB among cases with previous history of UTI was higher (53.8%) than cases with no history of UTI (46.2%), a statistical significant difference (p value<0.05) was found between bacteriuric and non-bacteriuric cases as regards history of previous UTI.
In about half the cases, the cause of preterm delivery is not known. However, accumulating evidence suggests that subclinical intrauterine infection with unknown etiology maybe responsible for the majority of cases.
Preterm infants are at risk for specific diseases such as respiratory distress syndrome, intraventricular hemorrhage, bronchopulmonary dysplasia, patent ductus arteriosus, necrotizing entericolitis, sepsis, apnea and retinopathy.
Preterm birth is the ultimate result of several different pathways that culminate in the initiation of labor before 37 weeks' gestation. It is useful to place preterm births in two broad categories- those that are obstetrically indicated and those that are spontaneous.
The pathogenesis of preterm labor is not well understood, and it is often not clear whether preterm labor represents early idiopathic activation of the normal labor process or results from a pathologic mechanism. So, preterm labor probably represents a syndrome rather than a specific diagnosis, since the causes are varied.
American College of Obstetricians and Gynecologists (1999) reported that the studies of the epidemiology and pathophysiology of preterm birth have identified four pathways leading to preterm labor and delivery:
1. Inflammation.
2. Decidual hemorrhage.
3. Uterine over-distention.
4. Premature activation of the normal physiologic initiators of labor.
The etiology of spontaneous preterm labor and preterm birth is multifactorial but there is overwhelming evidence that infection is an important cause, probably accounting for up to 30% of cases .There is accumulating evidence to support this: Pro inflammatory cytokines such as interleukin 1, 6 & 8 and tumor necrosis factor alpha are found significantly increased concentrations in the amniotic fluid of women in spontaneous preterm labor with infection compared to women without infection. The presence of these cytokines in amniotic fluid and fetal blood has been shown to be associated with fetal and neonatal tissue damage.
Controversy exists regarding the association between asymptomatic bacteriuria during pregnancy and adverse perinatal outcome, including preterm deliveries and low birthweight. Urinary tract infections are the most common medical complication of pregnancy. Asymptomatic bacteriuria is the most prevalent of these infections and it is defined as, the finding of greater than (100,000) colony forming units per mL of clean catch urine specimens or one catheterization specimen. Lower colony counts in asymptomatic women usually represent contamination.
Some physiological changes occurring during the pregnancy expedite the emergence of urinary infections and cause a higher incidence. As a result of hormonal changes, tonus of urinary bladder and ureter is reduced, and subsequently dilatation in the ureter and renal pelvis, incidence of urinary stasis and vesicourteric reflux increase. Increased plasma volume and glomerular filtration rate result in reduction in the urinary concentration. Furthermore, there is an increase in the incidence of glycosuria and aminoaciduria and a reduction in the resistance of urinary tract system against bacteria in pregnancy. Depending on all these developments, the incidence of symptomatic urinary tract infections is increased in pregnancy.
Early in pregnancy there is little impact of hormonal changes on the genitourinary tract and treatment considerations would likely be similar to those for uncomplicated UTI. Hormonal effects later in pregnancy lead to decreased autonomic muscle tone and stasis in the genitourinary tract. There is also an increased risk of reflux and obstruction with pressure of the fetal head at the pelvic brim. These physiological changes suggest management of infection later in pregnancy would be similar to complicated urinary infection. An additional consideration is that antimicrobial selection must consider the potential impact on the fetus.
The prevalence of asymptomatic bacteriuria during pregnancy ranges from about 2 to 12%. While rates from most recent observational studies done in developing countries fall within this range, the prevalence of asymptomatic bacteriuria was reported to be as high as 86.6% in a study from Nigeria, although S. aureus, which is not typically recognized as a uropathogens, made up over a third of the isolates.
Pregnant females with bacteriuria are at high risk of suffering recurrent bacteriuria; this, if left untreated, can cause pyelonephritis late in the pregnancy or puerperium. In the preantibiotic era, pregnant women with bacterial pyelonephritis had a high rate of infant prematurity and perinatal mortality.
In the Cochrane Review of antibiotic treatment for asymptomatic bacteriuria in pregnancy that included ten randomized controlled clinical trials where the outcome of preterm delivery or low birth-weight was reported, antibiotic treatment was shown to be associated with a reduction in this outcome. The mechanism for an association between preterm labor and asymptomatic bacteriuria has not been established, but a theoretical argument is made for a causative role for the production of phospholipase A2 by microorganisms, which then can initiate labor through the activation of prostaglandin. While this mechanism has been well defined for intra-amniotic infection and symptomatic pyelonephritis, there has been no recent research to explore the mechanisms through which asymptomatic bacteriuria exerts adverse pregnancy outcomes. Treatment of asymptomatic bacteriuria identified early in pregnancy decreases the risk of pyelonephritis later in pregnancy by at least 75%. Treatment of asymptomatic bacteriuria also significantly improves the adverse fetal outcomes of premature labor and low birth weight.
This study is a case control study conducted in Ain Shams University Maternity Hospital to investigate the association between asymptomatic bacteriuria and preterm labor. A total of third trimesteric 150 pregnant women were included in this study during the period from February 2012 till March 2013, they were divided into two groups, cases and Control group each 75 patients.
After comprehensive history taking and complete physical examination, clean catch midstream urine sample had been taken for urine culture and sensitivity.
Among the 150 women included in this study, 18 women had true culture bacteriuria giving a prevalence of 12%.
In our study, table 13 showed that prevalence of ASB among cases of preterm labor was 17.6% and among control was 6.7%.There is a statistical significant difference between cases and controls regarding ASB.
The microbiology of bacteriuria in this study (table 14) showed that E.coli was the most common pathogen (67% of the positive cultures) followed by staph aureus and proteus mirabilis. The antibiotic sensitivity patterns were showed in table 14, showing that most of the bacterial isolates were sensitive to nitrofurantoin 61% and cefoperazone 38.8%.
Prevalence of ASB among cases with previous history of UTI was higher (53.8%) than cases with no history of UTI (46.2%), a statistical significant difference (p value<0.05) was found between bacteriuric and non-bacteriuric cases as regards history of previous UTI.
Other data
| Title | A STUDY OF THE CORRELATION BETWEEN ASYMPTOMATIC BACTERIURIA AND PRETERM LABOR | Other Titles | دراسة العلاقة بين البيلة الجرثومية العديمة الأعراض والولادة المبكرة | Authors | Mostafa Mahmoud Mahmoud Ibrahim | Issue Date | 2015 |
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