Nutrition before, during and after pregnancy directly impacts the health of a mother and baby. Prior to becoming pregnant, women should achieve and maintain a healthy weight. If a woman is overweight or obese, she should follow a reduced-calorie diet until she achieves a healthy weight. Once pregnant, a woman's energy needs increase due to the growth and development of the fetus as well as maternal tissues and an increase in the mother's blood supply.
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Energy recommendations account for: the basal metabolic rate -- the energy needed to maintain metabolic activities within tissues and cells; the thermic effect of food -- the energy needed to digest and metabolize food; and the energy expended while physically active. Additional energy is required during pregnancy to support the demands pregnancy has on the mother's metabolism and fetal growth. During pregnancy, a woman's metabolism increases approximately 15 percent. The Institute of Medicine recommends that women consume an additional 340 calories per day during the second trimester and 452 calories above their normal energy needs each day during the third trimester.
Target Daily Calorie Levels
A moderately active 5-foot-4-inch-tall woman weighing 135 pounds requires approximately 1,800 calories to maintain her healthy weight. During pregnancy, her daily recommendation for energy would be 2,140 and 2,252 calories during the second and third trimesters, respectively. An overweight, moderately active 5-foot-4-inch woman would need approximately 150 calories more each day for a total of 1,950 prior to pregnancy, 2,290 calories during the second trimester and 2,402 calories during the third trimester. An obese woman at the same height would require about 2,500 and 2,750 calories per day during the second and third trimesters, respectively, to meet her basic energy needs as well as those of the developing fetus. During pregnancy, doctors may adjust calorie recommendations based on the rate at which a mother is gaining weight.
Maternal Weight Gain
The Institute of Medicine has different guidelines for total weight gain and rate of weight gain based on a mother's pre-pregnancy weight. Underweight women, or those with a body mass index of 18.5 or less, should gain 28 to 40 pounds; normal-weight women with a body mass index of 18.5 to 24.9 should gain 25 to 35 pounds throughout pregnancy, while overweight and obese women, who have a body mass index of 25 to 29.9 and 30 or more, respectively, should gain only 15 to 25 and 11 to 20 pounds. All women should gain a total of 1 to 4 pounds during the first trimester. During the second and third trimesters, underweight and normal-weight women should aim for approximately 1 pound of weight gain per week. Overweight and obese women should only gain about 1/2 pound each week during the second and third trimesters. Normal-weight women pregnant with twins should aim to gain 37 to 54 pounds; overweight women should gain 31 to 50 pounds; and obese women should gain 25 to 42 pounds.
Extra calories during pregnancy should be from nutritious foods, such as lean meats, low-fat or fat-free dairy products, fruits, vegetables and whole-grain breads and cereals. A pregnant woman needs at least 5 to 6 ounces of protein from lean meat, fish, poultry, beans, lentils, tofu, eggs or nuts. Three cups of low-fat or fat-free dairy products help meet calcium and vitamin D requirements. Other goals include eating at least 3 cups of vegetables, 2 cups of fruit and 5 to 7 ounces of grains each day.