Effects of carbon monoxide exposure on pregnant sows and their fetuses

Miniature and domestic sows at 108 to 110 days of the gestation were exposed to atmospheric carbon monoxide (CO) concentrations of 150 to 400 ppm for 48 to 96 hours. Overall stillbirth rates were 6.7%, 34.8%, 42.3%, and 80.0% in the sows exposed to CO in concentrations of 200, 250, 300, and 350 ppm, respectively. A significant linear relationship was determined between these concentrations of CO and the resultant maternal carboxyhemoglobin (COHb) concentration (P less than 0.01). The frequency of stillbirth increased significantly when maternal COHb concentration exceeded 23% saturation of hemoglobin. The COHb concentrations in new-delivered pigs (cesarean section) were greater than maternal COHb concentrations by 3 to 22%. Common gross lesions in stillborn pigs were cherry red discoloration of the subcutaneous tissues, muscle, and viscera and accumulation of a large volume of serosanguineous pleural effusion. Hypoxic ischemic leukoencephalopathy was found in new-delivered pigs from 3 of 14 litters. Lesions included focal leukoencephalomalacia, glial-vascular proliferation, multifocal hemorrhage, and vacuolation of the neuropile. Many extramedullary hematopoietic centers were present in liver sections.