Final answer:
During the 1st trimester of pregnancy, an active 24-year old woman does not need to consume additional calories. However, weight gain of 0.45 kg (1 lb) per month is common. During the 2nd and 3rd trimesters, an additional 300 calories per day are needed for the growing fetus.
Step-by-step explanation:
During the first trimester of pregnancy, an active 24-year old woman does not need to consume additional calories to maintain a healthy pregnancy. However, it is common to gain approximately 0.45 kg (1 lb) of weight per month during this trimester. The need for additional calories arises during the second and third trimesters, with an increase of about 300 calories per day to support the growing fetus. Most pregnant women gain approximately 0.45 kg (1 lb) per week during the later stages of pregnancy.