The discussion suggests that one might well expect CO to have larger effects than other pollutants because of its ability to cross the placenta and accumulate in the blood of the fetus.
However,pollution exposure could indirectly affect the fetus through the health of the mother by, for example, weakening her immune system.
Moreover, all three pollutants can directly affect infants after birth.
Although the available research points towards potential impacts, it provides little guidance about the necessary levels of pollution to induce negative effects or when fetuses or infants are most vulnerable.