What is the fetus's primary energy source?

• A. Glucose
• B. Protein
• C. Fat
• D. Amino acids

Answer: (A)

Glucose is the fetus’s primary energy source because it is the main fuel provided from the mother across the placenta. Glucose readily crosses the placental barrier and is readily used by fetal tissues for ATP production, supporting rapid growth and development. While amino acids are essential for building proteins and fats serve their structural roles, glucose dominates as the energy substrate in utero. In short, glucose fuels the fetus far more than fats or amino acids, making it the principal energy source.