Final answer:
Women carrying more than one fetus should be encouraged to gain an additional 300 calories per day during the second and third trimesters of pregnancy to support the growing babies.
Step-by-step explanation:
During pregnancy, women carrying more than one fetus are encouraged to gain an additional 300 calories per day to support the growing fetuses. This extra calorie intake is necessary during the second and third trimesters when the fetuses are growing most rapidly. However, doubling the caloric intake during pregnancy can lead to excessive weight gain, which can have negative health consequences for both the mother and the babies.