Background
Postpartum infections comprise a wide range of entities that can occur after vaginal and cesarean delivery or during breastfeeding. In addition to trauma sustained during the birth process or cesarean procedure, physiologic changes during pregnancy contribute to the development of postpartum infections. [1] The typical pain that many women feel in the immediate postpartum period also makes it difficult to discern postpartum infection from postpartum pain.
Postpartum patients are frequently discharged within a couple days following delivery. The short period of observation may not afford enough time to exclude evidence of infection prior to discharge from the hospital. In one study, 94% of postpartum infection cases were diagnosed after discharge from the hospital. [2] Postpartum fever is defined as a temperature greater than 38.0°C on any 2 of the first 10 days following delivery exclusive of the first 24 hours. [3] The presence of postpartum fever is generally accepted among clinicians as a sign of infection that must be determined and managed.
Pathophysiology
Local spread of colonized bacteria is the most common etiology for postpartum infection following vaginal delivery. Endometritis is the most common infection in the postpartum period. Other postpartum infections include (1) postsurgical wound infections, (2) perineal cellulitis, (3) mastitis, (4) respiratory complications from anesthesia, (5) retained products of conception, (6) urinary tract infections (UTIs), and (7) septic pelvic phlebitis. Wound infection is more common with cesarean delivery. (A review study by Haas et al indicated that cleansing the vagina with a povidone-iodine or chlorhexidine solution immediately prior to cesarean delivery decreases the risk for postoperative endometritis. [4, 5] )
Etiology
Endometritis
The route of delivery is the single most important factor in the development of endometritis. [6] The risk of endometritis increases dramatically after cesarean delivery. [6, 7] However, there is some evidence that hospital readmission for management of postpartum endometritis occurs more often in those who delivered vaginally. [7]
Other risk factors include prolonged rupture of membranes, prolonged use of internal fetal monitoring, anemia, and lower socioeconomic status. [6]
Perioperative antibiotics have greatly decreased the incidence of endometritis. [6]
In most cases of endometritis, the bacteria responsible are those that normally reside in the bowel, vagina, perineum, and cervix.
The uterine cavity is usually sterile until the rupture of the amniotic sac. As a consequence of labor, delivery, and associated manipulations, anaerobic and aerobic bacteria can contaminate the uterus.
Wound infections
Most often, the etiologic organisms associated with perineal cellulitis and episiotomy site infections are Staphylococcus or Streptococcus species and gram-negative organisms, as in endometritis.
Vaginal secretions contain as many as 10 billion organisms per gram of fluid. Yet, infections develop in only 1% of patients who had vaginal tears or who underwent episiotomies.
Those who underwent cesarean delivery have a higher readmission rate for wound infection and complications than those who delivered vaginally. [8]
Genital tract infections
Increased risk of genital tract infections is related to the duration of labor (ie prolonged labor increases risk of infection), use of internal monitoring devices, and number of vaginal examinations. [9]
Genital tract infections are generally polymicrobial. Gram-positive cocci and Bacteroides and Clostridium species are the predominant anaerobic organisms involved. Escherichia coli and gram-positive cocci are commonly involved aerobes.
Mastitis
The most common organism reported in mastitis is Staphylococcus aureus. The organism usually comes from the breastfeeding infant's mouth or throat.
Thrombosis
Thrombosis may occur. Numerous factors cause pregnant and postpartum women to be more susceptible to thrombosis. Pregnancy is known to induce a hypercoagulable state secondary to increased levels of clotting factors. Also, venous stasis occurs in the pelvic veins during pregnancy.
Although relatively rare, septic pelvic thrombosis is occasionally observed in the postpartum patient, who might have fever.
Urinary tract infections
Bacteria most frequently found in UTIs are normal bowel flora, including E coli and Klebsiella, Proteus, and Enterobacter species.
Any form of invasive manipulation of the urethra (eg, Foley catheterization) increases the likelihood of a UTI.
General risk factors
The following increase the risk for postpartum infections:
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History of cesarean delivery
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Premature rupture of membranes
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Frequent cervical examination (Sterile gloves should be used in examinations. Other than a history of cesarean delivery, this risk factor is most important in postpartum infection.)
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Internal fetal monitoring
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Preexisting pelvic infection including bacterial vaginosis
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Nutritional status
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Obesity
A retrospective study by Mitchell et al showed that women with a body mass index of 40 kg/m2 or higher who gained more than 20 lb during pregnancy had a threefold higher odds of postpartum infectious morbidity compared with obese women who gained less gestational weight. [10] An observational study by Axelsson et al found that women with class II or class III obesity were at increased risk for endometritis after normal vaginal delivery and for wound infections after cesarean section. [11]
In a study by Bauer et al, of approximately 45 million hospitalizations for delivery between 1998 and 2008, medical conditions that were found to be independently associated with severe sepsis included congestive heart failure, chronic kidney disease, chronic liver disease, and systemic lupus erythematosus. An association with rescue cerclage was also found. [12]
Epidemiology
United States statistics
In a study by Yokoe et al in 2001, 5.5% of vaginal deliveries and 7.4% of cesarean deliveries resulted in a postpartum infection. [2] The overall postpartum infection rate was 6.0%. Endometritis accounted for nearly half of the infections in patients following cesarean delivery (3.4% of cesarean deliveries). Mastitis and urinary tract infections together accounted for 5% of vaginal deliveries. [2]
The previously cited study by Bauer et al indicated that in the United States from 1998 to 2008, of approximately 45 million hospitalizations for delivery, sepsis was a complication in 1 out of every 3333 deliveries. The investigators also found that during the study period, the risk for severe sepsis (1:10,823 deliveries) and sepsis-related death (1:105,263 deliveries) increased. [12]
Race-related demographics
The risk of postpartum urinary tract infection is increased in the African American, Native American, and Hispanic populations. [13]
Prognosis
The prognosis for postpartum infections is good with prompt and appropriate therapy.
In most reviews, maternal death rates associated with infection range from 4-8%, or approximately 0.6 maternal deaths per 100,000 live births.
A pregnancy-related mortality surveillance by the Centers for Disease Control and Prevention indicated infection accounted for about 11.6% of all deaths following pregnancy that resulted in a live birth, stillbirth, or ectopic. [14]
Complications
Complications include the following:
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Scarring
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Sepsis
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Death
