Chapter 8: Pulmonary Edema in Pregnancy

INTRODUCTION

Pulmonary edema is defined as the abnormal accumulation of fluid in the interstitial and alveolar spaces of the lung. This accumulation can ultimately impair gas exchange by leading to decreased diffusion of carbon dioxide and oxygen in the alveoli. The resulting impact on oxygenation and ventilation carries significant morbidity and has the potential to be life threatening if severe.¹ It is important to note that pulmonary edema is a clinical symptom that represents the manifestations of several distinct pathological processes. In the setting of pregnancy, pulmonary edema is relatively rare, but it can present in patients in the antepartum, intrapartum, and postpartum periods.² Maternal pulmonary edema is particularly concerning as the parturient already has decreased pulmonary functional reserve because of the physiologic changes associated with pregnancy, increased metabolic needs, and the gestating fetus is less able to tolerate a hypoxic maternal environment. Furthermore, several coexisting maternal conditions and complications, such as underlying cardiac disease, preeclampsia, sepsis, multiple gestations, as well as routinely used treatments (eg, tocolysis) can lead to the development of pulmonary edema or worsen the severity of the condition.^2,3

INCIDENCE

Pulmonary edema occurring during pregnancy or in the postpartum period has a reported incidence of 0.08%.² Despite the low incidence of the disease, it is associated with a disproportionate amount of morbidity and mortality.⁴ The period of pregnancy at greatest risk for presentation appears to be the immediate postpartum. In the largest case series available from a high-volume tertiary care hospital (51 cases over 10 years and 62,917 pregnancies), 39% of cases presented in the first 24 hours following delivery. This compares with 47% of cases diagnosed in the entire antepartum period (mean gestational age of at presentation approximately 31 weeks). Only 14% of patients in this case series developed pulmonary edema during labor. This distribution of the timing for presentation of pulmonary edema is consistent with previous reports.^2,5

Several predisposing factors have been identified in women who develop pulmonary edema during pregnancy. The most common attributable causes are pre-existing cardiac disease (25.5% of all cases), tocolytic use (25.5%), iatrogenic fluid overload (21.5%), and preeclampsia (18%).² Patients with these risk factors should significantly raise clinical suspicion for pulmonary edema in the setting of new-onset respiratory compromise. Other less common risk factors for the development of pulmonary edema have been identified in some but not all retrospective analyses (Table 8-1).