Only 4 lbs of the total weight gain is due to the developing baby. The remainder is comprised of vital tissues and fluids that nourish and protect the fetus before and after birth. The components of weight gain are:

The fat stores that the expectant mother lays down during pregnancy have important roles. For example, they act as a safeguard against any periods of food shortage. The energy stored in the fat is also used in producing breast-milk. Additionally, body fat insulates and protects the growing baby. The fat stores of 4-9 lbs represent approximately 25,000 calories and can subsidize the extra metabolic needs of late pregnancy and breast feeding. These fat stores may not be fully used and this may contribute to residual weight gain after each pregnancy.

You don't need that many extra calories during pregnancy; 100-300 calories each day is usually enough. That translates to, for example, one large banana (100 calories), two crackers and cheese (200 calories), a small chicken sandwich (300 calories).

However, calorie needs vary considerably from person. For women who substantially reduce their exercise while pregnant, the need for extra calories may be minimal. Even towards the end of the pregnancy only 2400 calories are needed daily by the average woman (taking 2100 calories as the needs of the average non-pregnant woman).

While few extra calories are required during pregnancy, there is a greater demand for extra nutrients. It is important to choose nutrient-dense foods and to avoid high fat and calorie-dense foods such as cookies, confectionery and soft drinks.

Vitamin/mineral supplementation, particularly of iron, folic acid and zinc is usually prescribed as a safeguard.