Norepinephrine may cause fetal hypoxia and bradycardia because of:

• A. Vasodilation and increased placental blood flow
• B. Maternal tachycardia
• C. Vasoconstriction reducing uterine blood flow
• D. Direct fetal myocardial stimulation

Answer: (C)

Norepinephrine is a potent vasoconstrictor that tightens vascular smooth muscle, including the uterine arteries. This vasoconstriction reduces uteroplacental blood flow and placental perfusion, leading to fetal hypoxia. In response to hypoxia, the fetal heart rate often slows down, resulting in bradycardia. So the main mechanism behind fetal hypoxia and bradycardia is vasoconstriction reducing uterine blood flow.

Vasodilation would do the opposite and increase placental perfusion, so it’s not the effect here. Maternal tachycardia may occur with sympathetic stimulation but does not directly explain fetal hypoxia. Direct fetal myocardial stimulation would more likely cause fetal tachycardia, not bradycardia.