During the second trimester of pregnancy, there is a significant increase in maternal and fetal energy demands. An additional 340 kcal per day is recommended to support the growth of fetal tissues, placenta, and maternal changes such as increased blood volume. This caloric increase helps ensure optimal fetal development without excessive maternal weight gain. The 340 kcal recommendation balances energy needs and prevents complications related to undernutrition or overnutrition.

Reference: Williams Obstetrics, Cunningham FG, 25th Edition.