Which of the following cannot pass across the placenta?

(a) oxygen

(b) waste materials

(c) blood

(d) nutrients

Oxygen cannot pass through the placenta

The placenta is the structure that allows for transfer of wastes, oxygen, and

nutrients between the mother and the fetus. The fetal blood comes extremely

close to the maternal blood in the placenta, but there is no intermingling of fetal

and maternal blood. The fetus and mother can even have, and often do have,

different blood types.