Transplacental Diffusion of Carbon Monoxide in Human Subjects

The content of carbon monoxide in maternal and in foetal blood was studied at various times after exposure to CO in concentrations sufficient to produce COHb levels of about 15 per cent in the mother's blood. CO diffused slowly from maternal to foetal blood. When exposure to CO was brief, the readings in foetal blood did not attain the levels to which the concentrations in maternal blood had fallen until 3 to 5 hours after exposure. Even when sufficient CO was breathed to maintain the maternal COHb at about 15 per cent for 2 hours, the content of CO was still not quite so high in foetal as in maternal blood. The disappearance of CO was somewhat slower from foetal blood than from maternal blood.