During the catabolic phase of pregnancy, which statement best describes maternal and fetal energy metabolism?

During the catabolic phase of pregnancy, which statement best describes maternal and fetal energy metabolism?

• A. Maternal energy needs met by fat; fetal energy needs met by glucose; maternal insulin resistance increases causing insulin sensitivity to decrease 50 to 70%; this promotes transfer of glucose to the fetus.
• B. Maternal energy needs and fetal energy needs are both met primarily by glucose produced by the liver.
• C. Insulin sensitivity increases during pregnancy, reducing glucose transfer to the fetus.
• D. Fetal glucose transfer to the mother is increased, while maternal energy is met by protein breakdown.

Answer: (A)

In the catabolic phase of pregnancy, the body shifts to make glucose available for the fetus while using fat stores to meet the mother’s energy needs. Placental hormones cause maternal insulin resistance, which lowers the mother’s use of glucose and raises circulating glucose levels. This rise in maternal blood glucose is what feeds the fetus through the placenta, ensuring the fetus has a steady glucose supply for growth. At the same time, the mother mobilizes fat stores so her energy comes mainly from fat rather than from glucose. The net effect is fetal energy is primarily glucose-driven, while maternal energy relies on fat, with insulin resistance increasing (a decrease in insulin sensitivity by roughly 50–70%) to promote glucose transfer to the fetus. Other statements don’t fit this pattern: insulin sensitivity does not increase during pregnancy; fetal glucose transfer to the mother does not increase (it’s the fetus that benefits from maternal glucose); and while gluconeogenesis can involve amino acids, maternal energy in this phase is dominated by fat breakdown rather than protein, making the described balance of substrates incorrect.

In the catabolic phase of pregnancy, the body shifts to make glucose available for the fetus while using fat stores to meet the mother’s energy needs. Placental hormones cause maternal insulin resistance, which lowers the mother’s use of glucose and raises circulating glucose levels. This rise in maternal blood glucose is what feeds the fetus through the placenta, ensuring the fetus has a steady glucose supply for growth. At the same time, the mother mobilizes fat stores so her energy comes mainly from fat rather than from glucose. The net effect is fetal energy is primarily glucose-driven, while maternal energy relies on fat, with insulin resistance increasing (a decrease in insulin sensitivity by roughly 50–70%) to promote glucose transfer to the fetus.

Other statements don’t fit this pattern: insulin sensitivity does not increase during pregnancy; fetal glucose transfer to the mother does not increase (it’s the fetus that benefits from maternal glucose); and while gluconeogenesis can involve amino acids, maternal energy in this phase is dominated by fat breakdown rather than protein, making the described balance of substrates incorrect.