sentences:  In humans, a certain subtype of cells of the placenta, namely the extravillous trophoblasts, express the enzyme and secrete it into the blood stream of a pregnant woman.Lowered diamine oxidase values in maternal blood in early pregnancy might be an indication for trophoblast-related pregnancy disorders like early-onset preeclampsia.Normally the enzyme is not or only very scarce present in the blood circulation of humans, but it increases vastly in pregnant women suggesting a protective mechanism against adverse histamine.