Pregnancy-related deaths, as reported by the Pregnancy Mortality Surveillance System, have steadily increased in the United States (US) from 7.2 deaths per 100,000 live births in 1987 to a high of 17.8 deaths per 100,000 live births in 2011.¹ Of the reported deaths within a year of pregnancy completion, 12.7% were related to infection or sepsis, with the distribution of mortality causes being relatively stable over recent years. Infection remains the fourth leading cause of maternal death in the United States.¹ Several studies from high-income countries report a maternal mortality rate due to sepsis of 0.1 to 0.6 per 1,000 deliveries, and sepsis accounts for 75,000 maternal deaths annually in low-income countries.²

The most common causes of postpartum infection include genital tract infections (such as endometritis, septic pelvic thrombophlebitis [SPT], and pelvic abscess), urinary tract infection (UTI), mastitis, breast abscess, and, although rare, epidural abscess and meningitis (Figure 30.1).³ Risk factors include mode of delivery, emergent delivery, immunocompromised state, and socioeconomic
status.³ Anemia is a risk factor and is thought to be related to poor nutrition or low socioeconomic status.³ Advanced age and body mass index (BMI) are both associated with increased prevalence of postpartum infections.⁴ Other risk factors include diabetes and labor prior to cesarean section.³ The risk of infection is higher in lower resource settings where other infections such as malaria, typhoid, and tetanus are also prevalent.

The postpartum period, also referred to as the puerperium, is by consensus defined as the time after delivery of the placenta (end of third stage of labor) until a minimum of 6 to 12 weeks postpartum when maternal physiologic characteristics are expected to fully return to the prepregnancy state. Some experts define this period to be up to 12 weeks postpartum because physiologic changes may persist.⁵ The US Joint Commission on Maternal Welfare defines postpartum fever as an oral temperature ≥ 100.4°F (38.0°C) on any two of the first 10 days postpartum. In the first 24 hours after delivery, low-grade fevers can be common and likely inflammatory in etiology. The fever is likely to resolve spontaneously, especially after vaginal birth or with misoprostol use. In practice, any maternal fever postpartum warrants a thorough physical examination, with persistent fever following the first 24 hours requiring a comprehensive evaluation including a thorough physical examination, complete blood count (CBC), blood cultures, urinalysis, urine culture, and initiation of antibiotics based on the leading differential diagnosis. Further laboratory testing is individualized based on a specific patient’s presentation and physical examination findings. Postpartum infections are differentiated by history as well as physical examination and supported by laboratory and imaging studies as indicated.

Endometritis is the most common cause of postpartum infection. Women undergoing cesarean sections have a 5- to 20-fold increased risk of postpartum infection compared to women who have vaginal deliveries.⁶ The incidence of endometritis is reported to be 1% to 3% following a vaginal delivery and up to 27% following cesarean sections, even with prophylactic antibiotics.^3,7

Patients typically present with a fever in the postpartum period. Additional symptoms may include abdominal or breast pain, foul-smelling discharge from the vagina or an incision, vaginal bleeding, malaise, nausea and vomiting, or systemic signs of infection. Patients may also report dysuria, hematuria, flank pain, shortness of breath, or cough. The workup and management are directed by the history and physical examination findings.

Endometritis is an ascending polymicrobial infection that occurs most often within 1 week postpartum. It is the most common cause of postpartum infection. In a study of postpartum women who did not receive any prophylactic antibiotics, the most commonly isolated organisms were Gardnerella vaginalis, Peptococcus species, Bacteroides species, Staphylococcus epidermidis, group B streptococcus, and Ureaplasma urealyticum.⁹ Delayed presentation between 1 and 6 weeks may occur and data suggest that in late-onset postpartum endometritis, such as 2 to 3 weeks postpartum, Chlamydia trachomatis is the most prevalent organism.^10,11

In immunosuppressed patients, such as patients with HIV infection, other less common pathogens may be isolated including herpes simplex virus and cytomegalovirus.⁸ Rare pathogens that may cause severe morbidity and mortality should be included in the differential of patients with persistent fevers or an aggressive course of disease. These include Clostridium sordellii (C. sordellii), Clostridium perfringens or streptococcus (namely group A streptococcus). Staphylococcus
toxic shock syndrome must also be considered. Several cases of postpartum endometritis caused by C. sordellii are reported, with an almost 70% mortality rate.^12,13 Reported signs and symptoms include sudden onset of influenza-like symptoms in previously healthy women, progressive refractory hypotension, local and spreading tissue edema, and absence of fever but with laboratory findings including marked leukocytosis and elevated hematocrit, usually from toxic shock.¹²

In the case of streptococcal infection, common isolates in order of decreasing prevalence are group B, group D enterococci, group D nonenterococci, Streptococcus pneumoniae, and Streptococcus viridans.¹⁴ The clinical presentation includes early-onset fever, often with few localizing signs, with good correlation between blood and genital isolates.¹⁴

The single most common risk factor for endometritis is cesarean delivery, particularly cesarean sections performed during the second stage of labor. Without antibiotic prophylaxis, the risk of endometritis is estimated at 3.5% among women undergoing elective cesarean section and as high as 28% among women who have a cesarean section following the onset of labor; with antibiotic prophylaxis, the risk is reduced to 1.7% and 11%, respectively.^6,15 Additional risk factors are listed in Table 30.1.

The diagnosis of endometritis is based on the patient’s history in correlation with the physical examination and laboratory findings. Patients may report fevers with or without chills, malaise, increased abdominal pain, foul-smelling vaginal discharge, or vaginal bleeding. Fever and tachycardia raise suspicion for infection. On examination, tenderness of the uterine fundus is concerning for endometritis. Other sources of infection should be ruled out. Laboratory investigations may show a leukocytosis. Universal blood cultures for all febrile intrapartum and postpartum patients are recommended despite blood cultures not often changing management as antibiotic selection, is tailored toward polymicrobial treatment. In patients with abrupt or unusual presentation, blood cultures may reveal more virulent causes of postpartum infection including group A streptococcus or C. perfringens.

In patients presenting with delayed postpartum endometritis or those with heavy vaginal bleeding, ultrasound imaging is useful to evaluate for the presence of retained products of conception, which often requires an evacuation procedure (dilation and curettage). Imaging is also indicated in patients who show no clinical improvement within 48 hours of treatment initiation.

The pathologic diagnosis of endometritis is very nonspecific and does not always correlate with clinical endometritis.¹⁶ Endometrial culture is seldom performed due to the high risk of contamination through the cervical canal. Further, the etiology is usually polymicrobial and delayed treatment while awaiting culture results is not recommended and seldom will change management.

Empiric antibiotic therapy is tailored toward covering a polymicrobial infection. Intravenous broad-spectrum antibiotics are recommended as initial therapy and should aim to cover the most common pathogens including facultative and anaerobic species. In general, a combination of ampicillin, gentamicin, and clindamycin is a good option for polymicrobial coverage. In patients with signs of severe infection, piperacillin/tazobactam is a reasonable alternative choice.

Wound infections are reported in 2.5% to 16% of patients postcesarean sections and tend to occur between 4 and 7 days postprocedure. However, infections can be delayed 2 to 3 weeks postpartum. Perineal infections usually involve previously repaired lacerations or episiotomies that lead to wound breakdown. These usually involve skin or gastrointestinal flora depending on the location. Infections are commonly limited to the laceration; however, they may progress to involve the surrounding skin, causing cellulitis, abscess, and in some rare cases necrotizing fasciitis.¹⁷ Worsening infections may track into the ischiorectal fossa and present as buttock pain.¹⁸

Relative to vaginal birth, cesarean sections carry a 5- to 20-fold increased risk of wound infection.² This risk has been significantly reduced by the use of preincision antibiotic prophylaxis. A recent meta-analysis shows that the preoperative addition of vaginal cleansing with povidone iodine decreases the risk of wound infection.¹⁹ Additionally, a randomized controlled trial shows the addition of azithromycin to be superior to placebo for reducing infection in nonelective cesarean sections.²⁰