Pneumonia in the Pregnant Patient: A Synopsis

, and , Division of Pulmonary and Critical Care Medicine, Winthrop University Hospital, Mineola, NY

Disclosures

Medscape General Medicine. 1999;1(3) 

In This Article

Bacterial Pneumonia

The incidence of pneumonia is particularly high among pregnant women with certain predisposing antecedents, such as a history of smoking or respiratory disease.[8]

Clinical Presentation and Course

Clinically, the features of acute bacterial pneumonia present no differently among gravid and nonpregnant patients. Hopwood[8] reported that among 23 pregnant patients who developed pneumonia, all had prior upper respiratory tract infection and 20 had cough. Fever above 38.3°C (101°F) was seen in 18, while only 3 patients reported dyspnea and 5 had chills.[8] This low incidence of reported dyspnea is likely the result of the pregnant patient viewing dyspnea as a normal symptom rather than pathologic. Benedetti and coworkers[9] also examined the radiographic features of pneumonia in pregnancy and found a single lobar infiltrate in the overwhelming majority of patients. Only one patient in the series had a parapneumonic pleural effusion.

When complications of pneumonia do develop in the pregnant patient, they usually are a consequence of delayed diagnosis. In fact, Hopwood[8] recommends that all women with persistent upper respiratory distress have a chest radiograph.

The physician should be alert to any pregnant woman reporting cough, phlegm, nasal stuffiness or discharge, or shortness of breath. This last symptom is a confounding factor because dyspnea is often physiologic and normal in pregnancy. The physician needs to maintain a high index of suspicion for any pulmonary pathology in the pregnant woman. Often she will stay home and not consider seeking medical attention, expecting to feel short of breath because of the pregnancy, when in actuality, this could represent the clinical presentation of pneumonia or some other disease process.

Postpartum pneumonia is also well-described, particularly because acid aspiration (Mendelson's syndrome) was first documented as an important complication of obstetric anesthesia.[34,35] During labor and delivery aspiration is the most common cause of postpartum pneumonia.

There is ongoing debate regarding the clinical utility of classifying pneumonia as atypical versus typical in the pregnant population. The typical pneumonia syndrome with fever, purulent sputum, chills, and a lobar infiltrate is classically considered suggestive of pneumococcal or Haemophilus influenzae pneumonia. In contrast, the atypical pneumonia syndrome with low-grade fever, gradual onset, mucoid sputum and patchy or interstitial infiltrates suggests infection with the atypical pneumonia pathogens.[36] However, recent studies in nonpregnant patients indicate that Legionella infection can present with an overlap of clinical features common to both syndromes.[37] Additionally, when serious disease is present, Legionella is frequently the inciting pathogen.[37]

It is therefore prudent to treat serious pneumonia in this population empirically for both syndromes, regardless of clinical presentation. For patients with an uncomplicated, community-acquired pneumonia, it is reasonable to target therapy at pneumococcus, H influenzae, and possibly atypical agents, depending on a variety of clinical assessments. When bacterial pneumonia complicates influenza, the superinfection is most commonly due, in addition to pneumococcus and H influenzae, to invasion by Staphylococcus aureus and gram-negative bacteria (cocci and bacilli). Nosocomial pneumonia in these patients is still most often a gram-negative infection, while aspiration pneumonia involves anaerobes as well as gram-negative organisms.

Medical Management

The choice of antibiotic therapy in the pregnant patient with pneumonia is dictated by the same principles as in the nonpregnant patient -- the presence or absence of coexisting illness,[38] the severity of illness at presentation, and whether treatment will be instituted as an inpatient or outpatient.[37,39,40,11]. As with all medications, fetal toxicities, teratogenicity, and excretion in breast milk are major considerations in determining the appropriate choice of drugs.

Therefore, paramount in the choice of antibiotic therapy for any condition in the pregnant patient is the safety of the agent to the fetus. The penicillins, cephalosporins, and macrolides (excluding erythromycin estolate, because it has been associated with hepatotoxicity in mothers during the second half of pregnancy) are safe. Clindamycin is also probably a safe agent, although clinical experience is limited.[36,41] Current antibiotics available for treatment of community-acquired pneumonia include fluoroquinolones, macrolides, and beta-lactams, as well as aminoglycosides, tetracyclines, and some miscellaneous agents such as trimethoprim-sulbactam.

Penicillins are only 50% protein-bound and can cross the placenta to achieve fetal concentrations that are therefore 50% of maternal levels.[42] The cephalosporins cross the placenta less effectively but also appear to have no adverse effect on the fetus. Tetracyclines have been associated with risk of fulminant maternal hepatitis when given in the third trimester of pregnancy and also stain and deform the fetal teeth when given at any time during the pregnancy.[42] The neonate exposed to tetracyclines in utero may subsequently develop bony deformities. Sulfonamides administered shortly before delivery can cause fetal kernicterus, and the safety of trimethoprim is unknown. Chloramphenicol in the fetus, as in the adult, can lead to bone marrow suppression and even aplastic anemia. Use of chloramphenicol near term produces an adverse drug reaction known as "gray baby syndrome," which is characterized by ashen gray cyanosis, flaccidity, and cardiovascular collapse.[42]

Ideally once a specific pathogen is identified, therapy directed at the target organism can be started -- usually the etiologic agent at time of presentation is unknown, forcing the initial use of empiric treatment. Most patients with community-acquired pneumonia may be adequately treated with ampicillin or a cephalosporin, which will have coverage against pneumococcus, H influenzae, and some nonpseudomonal gram-negative bacteria (M catarrhalis, K pneumoniae, H influenzae, and E coli).

Consider the beta-lactams, such as penicillin -- while these are the drug class of choice for sensitive strains of S pneumoniae, no beta-lactam can provide coverage for organisms such as M pneumoniae, C pneumoniae, or L pneumophila -- all of which may be causative agents of community-acquired pneumonia, (often in the young patient who may have no comorbidities, such as is the case for most of the pregnant population). The first penicillin-resistant pneumococcus was isolated in 1967; since then, there has been a progressive rise. The incidence varies dramatically via geographical location -- the rates range from less than 5% (in Italy and the US ) and rise to as much as 70% (in Eastern Europe). Penicillin resistance propagates either by gene transfer or by clonal spread.

The penicillin-resistant pneumococci are frequently resistant to other antibiotics as well, including erythromycin, tetracyclines, and trimethoprim-sulbactam. Also, decreased susceptibility to cephalosporins is emerging.

Outcome of patients with S pneumoniae infection and a high rate of penicillin resistance appears not to be altered unless the host is immunocompromised -- therefore, particular care must be administered to the pregnant patient (clinical practice for those with mild to moderate pneumonia can reasonably include beta-lactam antibiotics -- ie, amoxicillin, cefotaxime, ceftriaxone, and imipenem). When the pneumococcus is highly resistant, glycopeptides, third-generation cephalosporins, and vancomycin are effective. As usual, the risk associated with therapy in pregnancy must be individualized for each patient.

The ATS-CAP[11]guidelines recommend second- or third-generation cephalosporins as treatment for those patients with community-acquired pneumonia requiring hospitalization. Third-generation cephalosporins such as ceftriaxone (Rocephin) or ceftazidime (Fortaz) are generally less active against pneumococcus species and anaerobes when compared to the second-generation cephalosporins such as cefuroxime. Cefotaxime (Claforan) and ceftriaxone have been successfully used in the treatment of community-acquired pneumonia in patients less than 60 years of age and without comorbidities -- which encompasses most of the pregnant population. The decision to add a macrolide in this instance is based on clinical suspicion of atypical infection -- and as discussed below, the newer macrolides can be added to increase coverage for suspected atypical pneumonia.

If an atypical pathogen is strongly suspected, a macrolide is the therapy of choice. The newer macrolides have proven extremely "attractive" in the treatment of community-acquired pneumonia, as they cover not only S pneumoniae and H influenzae, but also other atypical pathogens, namely M pneumoniae, C pneumoniae, and L pneumophila. Azithromycin is labeled category B in pregnancy. Studies in animals found no evidence of harm to the fetus associated with use of azithromycin -- thus allowing for its use during pregnancy. However, there are no adequate, well-controlled studies in pregnant women and because animal reproductive investigations may not be completely indicative of the human response, potential risk needs always to be weighed against benefit.

Clarithromycin is a pregnancy category C drug -- but this agent has also not been adequately evaluated in pregnant women. The physician needs to justify the indication for such antibiotics but can safely administer them at recommended doses in the pregnant woman.

Aminoglycosides should only be used if there is evidence of serious gram-negative infection, because the risk of ototoxicity to the fetus is significant. Similarly, vancomycin poses serious risk to the fetus -- it has been associated with fetal nephrotoxicity and ototoxicity; use of this agent must be carefully considered. Therapy with these agents can be monitored by following drug serum levels. Therefore, the antimicrobials that must be distinctly avoided in pregnancy are the tetracyclines, chloramphenicol, and all sulfa compounds.

Supportive therapy of the pregnant patient with pneumonia follows the same principles as used in the nongravid state; hydration, antipyretic therapy, and supplemental oxygen are key. The goal of oxygen therapy is more aggressive; maintenance of the arterial oxygen tension greater than 70mm Hg is critical because hypoxemia is less tolerated in the pregnant female. In addition, because respiratory alkalosis, a condition often associated with pulmonary disorders such as pneumonia, leads to reduction in uterine blood flow, the work of breathing must be decreased whenever possible in the pregnant pneumonia patient; adequate oxygenation is mandatory for this reason. Respiratory failure requiring mechanical ventilation has occurred in pregnancy and, therefore, close monitoring of both mother and fetus is required. Preterm labor is a well-documented complication of pneumonia, as previously mentioned, and may warrant tocolytic therapy.

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