URINARY TRACT INFECTIONS DURING PREGNANCY

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Urinary tract infections as a group are the most common medical complication of pregnancy. Although pregnancy, per se, does not predispose a woman to the acquisition of bacteria in the bladder (i.e., asymptomatic bacteriuria), it does predispose her to acute upper urinary tract infection or pyelonephritis. As discussed herein, the latter infection is associated with significant morbidity for the gravida and fetus.

Urinary tract infections are relatively common in women when compared with men. The major reason for this difference is probably anatomic. The female urethra is only 3 to 4 cm in length and lies in close proximity to the vagina, anus, and rectum, all of which are areas colonized with enteric flora (the Enterobacteriaceae).11

The pathogenesis of urinary tract infections is schematically illustrated in Figure 1.

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MICROBIOLOGY OF URINARY TRACT INFECTIONS

Most cases of urinary tract infections are caused by the Enterobacteriaceae, especially Escherichia coli and Klebsiella and Enterobacter spp. These organisms account for approximately 90% of all urinary tract infections encountered during pregnancy.9, 11, 21 Other commonly isolated uropathogens include Proteus, Pseudomonas, Citrobacter, Staphylococcus, and group B streptococcus. Group B streptococcal bacteriuria may be associated with early-onset neonatal sepsis. In a prospective study of group

RISK FACTORS FOR URINARY TRACT INFECTIONS

Socioeconomic status is the most significant risk factor, with medically indigent women having a fivefold greater incidence of bacteriuria than nonindigent populations.22, 29 When sickle cell status and socioeconomic status are controlled for, race, per se, does not seem to be associated with urinary tract infections in pregnancy. In a study of more than 8000 women receiving prenatal care, Pastore and colleagues24 reported that the presence of sickle cell hemoglobin almost doubled the risk

ASYMPTOMATIC BACTERIURIA

Asymptomatic bacteriuria is the most common urinary tract infection encountered during pregnancy, occurring in 2% to 7% of all pregnant women.21, 30 Asymptomatic bacteriuria is defined as the presence of significant bacteriuria in a woman without symptoms of urinary tract infection. Significant bacteriuria, in turn, is defined as 100,000 organisms per mL of urine or greater of a single uropathogen on a clean-voided specimen. Counts of less than 100,000 organisms per mL per specimen with two or

ACUTE CYSTITIS

Although the exact incidence of cystitis in pregnancy is unknown, Harris and Gilstrap16 reported an incidence of approximately 1% to 2% for their population. The diagnosis of cystitis is based on lower urinary tract symptoms in the presence of significant bacteriuria on culture. The signs and symptoms of acute cystitis in pregnant women are urgency, frequency, dysuria, hematuria, and pyuria.

The uropathogens associated with acute cystitis are the same as those causing bacteriuria. Moreover, the

ACUTE PYELONEPHRITIS

Acute symptomatic infection of the upper urinary tract is a major complication of pregnancy that may result in significant maternal and fetal morbidity. It has an incidence of approximately 1% to 2% during pregnancy and, in the presence of untreated bacteriuria, occurs in as many as 25% of pregnant women.10

As previously described (Fig. 1), the pathogenesis of acute pyelonephritis is related to the relative obstruction of pregnancy in association with bacteriuria. This obstruction is the result

SUMMARY

Urinary tract infections are relatively common in pregnancy and may result in significant morbidity for the pregnant woman and fetus. The authors recommend that all pregnant women be screened for the presence of bacteriuria at their first prenatal visit. Failure to treat bacteriuria during pregnancy may result in as many as 25% of women experiencing acute pyelonephritis. Women with acute pyelonephritis may sustain significant complications, such as preterm labor, transient renal failure, ARDS,

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    Address reprint requests to Larry C. Gilstrap III, MD, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Texas-Houston Medical School, 6431 Fannin, Suite 3.604, Houston, TX 77030

    *

    Department of Obstetrics, Gynecology and Reproductive Sciences, Division of Maternal-Fetal Medicine, University of Texas-Houston Medical School, Houston, Texas

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