Although pregnancy is infrequently complicated by pneumonia, lung infection by bacteria, viruses, and fungi can pose serious maternal and fetal hazards. Pneumonia may lead to preterm labor and certain infecting agents, most notably the HIV virus, can cross the placenta and lead to neonatal infection. There is some evidence that the incidence of pneumonia in pregnancy may be increasing among certain populations. In addition, infections caused by viruses (varicella and influenza) and fungal agents, ordinarily controlled by cell-mediated immunity, may be more virulent to pregnant women, thereby adding to maternal mortality. Beyond the influence of these pregnancy-induced changes in immunity, there are certain physiologic changes in pregnancy that make it more difficult for the pregnant woman to sustain any type of respiratory infectious insult. Certain types of pneumonias, particularly influenza and aspiration, may be avoided if patients at risk are identified and existing strategies for prevention are applied. When the pregnant women is treated for lung infection, the safety of antimicrobial agents must be considered, and therapy may differ from that used in the nonpregnant patient.
