Community acquired pneumonia (CAP) in pregnancy

1. What every clinician should know

Clinical features, incidence and risk factors

Clinical features of pneumonia in pregnancy resemble the disease in nonpregnant individuals. Fever, productive cough, pleuritic chest pain and dyspnea are the most common symptoms. Pregnant women may be at greater risk for morbidity and mortality due to pneumonia because of the immunologic and physiologic changes of pregnancy.

Additional risk factors for morbidity include smoking, asthma, immunosuppression and obesity.

Types of pneumonia to consider include community-acquired pneumonia (0.4-2.7/1000 births in large birth cohorts), viral pneumonia and aspiration pneumonia.

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2. Diagnosis and differential diagnosis

Establishing the diagnosis

Diagnosis is best made by clinical symptoms, physical exam and confirmation by chest X-ray. Important information to elicit in the history includes travel and specific exposures. In addition, consider national and international outbreaks such as H1N1 or SARS.

Physical exam: Rales and pulmonary changes such as dullness are often absent despite disease.

Chest X-ray patterns seen with bacterial CAP are generally areas of consolidation in one lobe or multilobar. Pleural effusions are uncommon. Patchy infiltrates are more suggestive of atypical pneumonia or viral etiologies.

Sputum culture and gram stain to identify the organism may be useful in determining therapy but is often negative. If women are ill, blood cultures may be useful. Urine antigen tests for S. pneumoniae and Legionella species may be important in some women.

Community acquired pneumonia may be caused by Streptococcus pneumoniae, Hemophilus influenzae, Staphylococcus aureus (may be methicillin-resistant) and Pseudomonas aeruginsa. Atypical agents such as Legionella species, Mycoplasma pneumoniae and Chalmydophila pneumoniae also are seen. Viruses that may cause CAP include influenza A and B, and varicella. Other less common organisms include fungi, pneumocystis carinii and coccidiomycosis. In assessing the likelihood for other unusual organisms, a travel history to document certain exposures may be critical.

Additional tests that may be helpful include pulse oximetry to indicate hypoxemia even in a well appearing pregnant woman. Bronchoscopy and bronchoalveolar lavage can be reserved for critically ill women or those who have not responded to initial antibiotic therapy.

Disease severity scores are routinely used in adult patients with pneumonia to determine need for hospitalization as well as need for ICU care. Although validated in adults, these scores have not been used in pregnancy. Most pregnant women with pneumonia are hospitalized for IV antibiotics and observation given the high risk for maternal and fetal morbidity.

Differential diagnosis

The differential diagnosis for community acquired pneumonia may include pyelonephritis with ARDS, pulmonary edema, bronchitis, asthma, chest mass originating in the lung parenchyma or lymph nodes, pulmonary embolus, cardiomyopathy, reflux and other pulmonary disease such as tuberculosis. As noted above, chest X-ray, bronchoscopy and history are most useful in sorting through the list of diagnoses.

Aspiration pneumonia is generally seen as a postoperative complication. Oral flora and/or gastric contents in the lung space can lead to tachypnea, pulmonary edema, spasm and a diffuse pneumonitis picture on chest X-ray.

Fungal pneumonias may complicate disseminated infections such as coccidioidomycosis. This organism is generally seen in the southwestern United States. These patients may present with fever, cough, headache, malaise and erythema nodosum. Others at high risk for unusual pathogens are women with immune suppression such as HIV infected individuals with low CD4 counts who are risk for Pneumocystis jirovecii.

3. Management

The mainstay of management for pneumonia is prompt antibiotic therapy. Empiric antibiotics that include beta lactams such as cefotaxime or ceftriaxone or ampicillin- sulbactam plus azithromycin will cover the most likely organisms for CAP. Avoid fluoroquinolones and doxycycline. If pseudomanas coverage is needed, consider an antipseudomonal beta lactam such as cefopime, imepenem, piperacillin-tazobactam plus an aminoglycoside plus azithromycin.

If influenza A, prompt therapy with oseltamavir is indicated without confirmation of the presence of flu. If varicella pneumonia, prompt therapy with acyclovir is indicated. Clinical response to therapy is expected in 48-72 hours; however, resolution of symptoms and chest X-ray findings may lag. Once there is clinical improvement after IV therapy, transition to oral antibiotics to complete a 7-10 day course of antibiotics is adequate.

Treatment failures may require a reassessment of the antibiotic choice. Although it is appropriate to reculture the sputum, it is important to interpret the results with caution and the knowledge that the upper respiratory tract may be colonized with organisms not causing the pneumonia. If there is suspected treatment failure, consider repeating the history to elucidate suspicious exposures or travel history. In addition, bronchoscopy with lavage may be helpful.

Antipyretics and careful fluid management are important for pregnant women who are prone to leaky capillaries. Continuous pulse oximetry may be useful along with continuous fetal monitoring for viable fetuses when preterm labor is apparent or maternal hypoxemia has not been corrected.

Intrapartum and postpartum therapy is the same. Fluoroquinolones and doxyclyline may be used in the absence of breastfeeding instead of azithroymycin.

4. Complications

Maternal complications of pneumonia include respiratory failure, pulmonary edema, ARDS and hypoxemia. Women with viral pneumonia also may develop superimposed bacterial infections.

Fetal issues may arise in the setting of preterm labor, premature rupture of the membranes and preterm delivery. Some studies show that in addition to preterm labor and delivery, fetal growth restriction is also a potential long term outcome for these exposed fetuses.

Fluid management is critical to minimize the risk of pulmonary edema. Antipyretics are indicated to reduce the amount of time the baby is exposed to fever; however, infection may increase the susceptibility to Tylenol toxicity and Tylenol dosing should be monitored.

5. Prognosis and outcome

Most studies of antibiotic therapy for pneumonia show that therapy begun as early in the course as possible is associated with the best prognosis. This is important for bacterial, atypical and viral pneumonias. For example, the death rate from H1N1 in pregnancy was highest among pregnant and postpartum women in whom antiviral therapy was delayed awaiting confirmation of influenza. In addition, there were more admissions to the ICU for respiratory failure needing ventilatory support in the group who were started on antiviral therapy days after presentation.

Prevention is the mainstay of protecting adults from pneumonia. Influenza vaccination using inactivated virus is recommended for all pregnant women yearly regardless of gestational age during influenza season. Pneumococcal vaccination is recommended for pregnant women with certain high risk conditions, including: smoking; renal, cardiovascular or liver disease; diabetes mellitus; CSF leaks; alcoholism; or asplenia. Varicella vaccine is recommended for women postpartum if they have not had chicken pox or been previously vaccinated.

6. What is the evidence for specific management and treatment recommendations

Mandell, LA, Wunderink, RG, Anzueto, A. “Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults”. Clin Infect Dis. vol. 44. 2007. pp. S27(These guidelines review the evaluation and management of adults presenting with community acquired pneumonia and focus on appropriate antibiotic choices for empiric therapy as well as location for treatment. These guidelines are not specific for pregnancy.)

Sheffield, JS, Cunningham, FG. “Community-acquired pneumonia in pregnancy”. Obstet Gynecol. vol. 114. 2009. pp. 915(This is a comprehensive review of pneumonia in pregnancy that discusses the IDSA/ATS guidelines in the context of pregnancy. In addition, there is in depth discussion of the presentation of pneumonia in pregnancy as well as the fetal outcomes.)

Siston, AM, Rasmussen, SA, Honein, MA. “Pandemic 2009 Influenza A(H1N1) Virus Illness Among Pregnant Women in The United States”. JAMA. vol. 303. 2010. pp. 1517(Retrospective review of 788 pregnant women reported to have H1N1 of which 5% died and 22.6% were admitted to the ICU. This data reveals the presentation and result of treatment delay for pregnant and postpartum women infected with H1N1 in 2009.)

Brito, V, Niederman, MS. “Pneumonia Complicating Pregnancy”. Clin Chest Med. vol. 32. 2011. pp. 121-32. (Excellent review of pneumonia complicating pregnancy with in-depth discussion of most common organisms encountered and clinical presentation.)