Pneumonia is inflammation affecting the lung parenchyma distal to the larger airways and involving the respiratory bronchioles and alveolar units. Pneumonitis causing an appreciable loss of ventilatory capacity is tolerated less well by women during pregnancy. This generalization seems to hold true regardless of the etiology of the pneumonia. Moreover, hypoxemia and acidosis are poorly tolerated by the fetus, and they frequently lead to preterm labor. Because many cases of pneumonia follow common viral upper respiratory illnesses, worsening or persistence of symptoms may represent developing pneumonia. Any pregnant woman suspected of having pneumonia should undergo anteroposterior and lateral chest radiography.
Pregnancy itself does not predispose to pneumonia. The incidence of pneumonia complicating pregnancy is approximately 1.5 per 1000, and at least half are bacterial. The most common organism is Streptococcus pneumoniae. Other bacterial causes include Mycoplasma pneumoniae and Haemophilus influenzae. Chlamydophila pneumoniae is also a significant cause of pneumonia during pregnancy.
Typical symptoms of pneumonia include cough (90 percent of cases), dyspnea (65 percent), sputum production (65 percent), and pleuritic chest pain (50 percent). Upper respiratory symptoms and malaise usually precede these symptoms. There usually is mild leukocytosis. Chest x-ray is essential for diagnosis, although its appearance does not accurately predict the etiology (Figure 49-1).
FIGURE 49-1 Chest radiograph showing right lobar pneumonia caused by pneumococcal infection.
The responsible pathogen is identified in perhaps only half of cases. According to the Infectious Diseases Society of America and the American Thoracic Society, tests to identify a specific agent are optional. Thus, sputum cultures, serological testing, cold agglutinin identification, and tests for bacterial antigens are not recommended. The one exception may be rapid serological testing for influenza A and B.
The decision for hospitalization is perhaps the single most important decision for the management of community-acquired pneumonia. Risk factors shown in Table 49-1, especially if multiple, should prompt hospitalization. Initial hospitalization can serve to allow close observation for the first day or so to be sure that infection is responsive to therapy and that pulmonary function does not deteriorate.
TABLE 49-1. Criteria for Severe Community-Acquired Pneumonia
Antimicrobial treatment is empirical. Because the majority of cases of adult pneumonia are caused by pneumococci, mycoplasma, or chlamydophilia, a macrolide, like erythromycin, azithromycin, or clarithromycin is the logical choice in the uncomplicated case. The usual dose of erythromycin is 500 to 1000 mg every 6 hours, and this can be given intravenously, at least initially.
For women with the complications listed in Table 49-1, cefuroxime or ceftriaxone is given in addition to a macrolide. Monotherapy with antipneumococcal drugs such as the fluoroquinolones—including moxifloxacin, gemifloxacin, levofloxacin, and others—is also acceptable. In some areas, as many as 25 percent of pneumococcal isolates are resistant to macrolides. Because very few of these are also resistant to fluoroquinolones, treatment with fluoroquinolones is recommended. The teratogenicity risk of fluoroquinolones is low, and these should be given if indicated. If community-acquired methicillin-resistant Staphylococcus aureus is suspected, then vancomycin should be added.
Clinical improvement is usually evident by 48 to 72 hours. Fever typically lasts 2 to 4 days. If fever persists, follow-up radiography should be considered. It is common for radiographic findings to worsen initially, and radiographic abnormalities may take up to 6 weeks to completely resolve. About 20 percent of cases have an associated effusion; however, with mild clinical disease that is improving, such findings are inconsequential. Conversely, radiographic deterioration in the setting of severe community-acquired pneumonia is a poor prognostic feature. Therapy is recommended for at least 5 days, and treatment failure may occur in 15 percent of cases.
Pneumococcal vaccine has been shown to be 60 to 70 percent protective against the 23 vaccine-related serotypes. The vaccine is not given to otherwise healthy pregnant women. It is recommended, however, for immunocompromised adults including those with human immunodeficiency virus (HIV) infection, and those patients with a significant smoking history. It is also given to those who have underlying diabetes, cardiac, pulmonary, or renal disease as well as to those with asplenia or sickle-cell disease.
Respiratory infection including pneumonitis is caused by RNA viruses of which influenza A and B form one genus. Influenza infection can be serious, and it is epidemic in the winter months. The virus is spread by aerosolized droplets and quickly infects ciliated columnar epithelium, alveolar cells, mucus gland cells, and macrophages. If uncomplicated, the usual clinical course is 2 to 5 days.
In most healthy adults, infection is self-limited, but pneumonia is the most common complication. Clinically, it is difficult to distinguish influenza from bacterial pneumonia. Primary pneumonitis is the most severe form, and it is characterized by sparse sputum production and radiographic interstitial infiltrates (Figure 49-2). Secondary bacterial pneumonia is more common and usually is caused by streptococci or staphylococci. Secondary infection usually manifests after 2 to 3 days of clinical improvement.
FIGURE 49-2 Chest radiograph taken at admission in a 27-week pregnant woman with presumed viral pneumonia. Diffuse infiltrates are seen. These worsened, respiratory failure developed, and she died a week later. (Reproduced, with permission, from Richey SD, Roberts SW, Ramin KD, et al: Pneumonia complicating pregnancy. Obstet Gynecol 84:525, 1994.)
The Centers for Disease Control and Prevention and the American College of Obstetricians and Gynecologists (Committee on Obstetric Practice. Influenza vaccination and treatment during pregnancy. Obstet Gynecol. 2004; 104(5 pt 1):1125–6) recommend attenuated influenza vaccination for all women, regardless of trimester, who will be pregnant during influenza season, which is October through mid-May.
There is no evidence that inactivated influenza vaccine is teratogenic. Live attenuated vaccine for intranasal administration (FluMist) is contraindicated in pregnant women.
Generally, supportive treatment with antipyretics and bed rest is recommended for uncomplicated influenza. The neuraminidase inhibitor, Oseltamivir, 75 mg twice daily, is effective in reducing the severity of infection if begun within 48 hours of symptoms. It may also be given prophylactically to high-risk non-immunized exposed women to reduce the chance of clinical infection. There is little data on the use of antivirals for influenza in pregnancy, but the drugs are considered low risk. Providers are encouraged to review the CDC guidelines regularly for information about predominate strains and resistance to antivirals.
Varicella-zoster virus is a member of the DNA herpesvirus family, and almost 95 percent of adults are immune. Primary infection causes chickenpox, which has an attack rate of 90 percent in seronegative individuals. In the healthy patient, the typical maculopapular and vesicular rash is accompanied by constitutional symptoms and fever for 3 to 5 days. If infection develops before 20 weeks, the fetus can be infected and permanent sequelae may result.
Although secondary skin infection with streptococci or staphylococci is the most common complication of chickenpox, varicella pneumonia is the most serious. It develops in about 5 percent of adults. It usually appears 3 to 5 days into the course of the illness and is characterized by tachypnea, dry cough, dyspnea, fever, and pleuritic chest pain. Chest x-ray discloses characteristic nodular infiltrates and interstitial pneumonitis (Figure 49-2). In fatal cases, the lungs show scattered areas of necrosis and hemorrhage. Although resolution of pneumonitis parallels that of the skin lesions, fever and compromised pulmonary function may persist for weeks.
Women with varicella pneumonitis are hospitalized and treated with intravenous acyclovir, 10 to 15 mg/kg every 8 hours.
Administration of varicella-zoster immunoglobulin (VZIG), an experimental protocol not currently available in the United States, will either prevent or attenuate varicella infection in exposed susceptible individuals if given within 96 hours. Up to 80 to 90 percent of adults are immune from prior symptomatic or asymptomatic infection; thus, antibody testing with enzyme-linked immunosorbent assay (ELISA) or fluorescent antibody to membrane antigen (FAMA) should be done, if possible, prior to immune globulin therapy.
An attenuated varicella live-virus vaccine (Varivax) is recommended for susceptible adults. However, the vaccine is contraindicated in pregnancy.
The most common infectious complication in women with acquired immunodeficiency syndrome (AIDS) is interstitial pneumonia caused by the parasite Pneumocystis jiroveci. In immunocompromised patients, this is a life-threatening infection, and since the AIDS epidemic began in the 1980s, it is a common complication (see Chapter 85). Symptoms include dry cough, tachypnea, and dyspnea, and the characteristic radiographic finding is a diffuse infiltrate. Although the organism can be identified by sputum culture, bronchoscopy with lavage or biopsy may be necessary. Maternal mortality may be quite high.
Treatment is with trimethoprim-sulfamethoxazole or pentamidine. Both drugs are category C. In some cases, tracheal intubation and mechanical ventilation may be required.
For some HIV-positive patients, the Centers for Disease Control and Prevention recommend prophylaxis against pneumocystis infection with once-daily double-strength oral trimethoprim-sulfamethoxazole. These patients include women with CD4+ T-lymphocyte counts less than 200/μL, those with a history of oropharyngeal candidiasis, or those in whom CD4+ cells constitute less than 14 percent of lymphocytes.
For further reading in Williams Obstetrics, 23rd ed.,
see Chapter 46, “Pulmonary Disorders.”