Cocaine use during pregnancy negatively impacts fetal oxygenation by which mechanism?

• A. Reducing uterine blood flow
• B. Causing fetal bradycardia
• C. Delaying fetal lung maturation
• D. Increasing fetal metabolism

Answer: (A)

Cocaine restricts fetal oxygenation mainly by causing uteroplacental vasoconstriction. It blocks reuptake of norepinephrine, triggering sympathetic overactivity that constricts uterine and placental vessels, reducing blood flow to the placenta. With less blood reaching the fetus, oxygen transfer declines, risking fetal hypoxia and acidosis. Placental abruption can further worsen oxygen delivery in cocaine exposure.

Fetal bradycardia isn’t the primary mechanism because cocaine more commonly causes sympathetic-mediated tachycardia rather than a primary decrease in heart rate. Delaying fetal lung maturation is a developmental issue more related to preterm exposure and not the immediate oxygen delivery problem. Increasing fetal metabolism would raise oxygen demand, but the immediate deficit comes from reduced oxygen supply due to diminished uteroplacental blood flow.