What is the primary physiological effect of smoking during pregnancy on fetal oxygen transport?

What is the primary physiological effect of smoking during pregnancy on fetal oxygen transport?

• A. Carbon monoxide from smoke binds to maternal and fetal hemoglobin, decreasing oxygen binding
• B. It increases maternal blood flow and oxygen delivery to the fetus
• C. It has no effect on oxygen transport to the fetus
• D. It increases placental diffusion of oxygen to the fetus

Answer: (A)

The main concept is that carbon monoxide from cigarette smoke directly interferes with how oxygen is carried to the fetus. Carbon monoxide binds to hemoglobin much more readily than oxygen, forming carboxyhemoglobin. This reduces the blood’s capacity to carry oxygen and, because the bond is strong, also makes it harder for oxygen to be released to fetal tissues. The net effect is fetal hypoxia, since less oxygen reaches the developing baby. Nicotine can contribute by causing vasoconstriction of placental vessels, which further decreases oxygen delivery, but the primary transport problem is the formation of carboxyhemoglobin that blocks oxygen binding and release. The choices suggesting increased maternal blood flow or increased placental diffusion are not correct, and claiming there’s no effect ignores this critical mechanism.

The main concept is that carbon monoxide from cigarette smoke directly interferes with how oxygen is carried to the fetus. Carbon monoxide binds to hemoglobin much more readily than oxygen, forming carboxyhemoglobin. This reduces the blood’s capacity to carry oxygen and, because the bond is strong, also makes it harder for oxygen to be released to fetal tissues. The net effect is fetal hypoxia, since less oxygen reaches the developing baby.

Nicotine can contribute by causing vasoconstriction of placental vessels, which further decreases oxygen delivery, but the primary transport problem is the formation of carboxyhemoglobin that blocks oxygen binding and release. The choices suggesting increased maternal blood flow or increased placental diffusion are not correct, and claiming there’s no effect ignores this critical mechanism.