WEIGHT GAIN DURING PREGNANCY
Weight gain during pregnancy is natural and necessary for the infant to develop normally and the mother to retain her health. In addition to the developing in-fant, the mother’s uterus, breasts, placenta, blood volume, body fluids, and fat must all increase to accommodate the infant’s needs (Table 11-1).
The average weight gain during pregnancy is 25 to 35 pounds. During the first trimester of pregnancy, there is an average weight gain of only 2 to 4 pounds. Most of the weight gain occurs during the second and third tri-mesters of pregnancy, when it averages about 1 pound a week. This is because there is a substantial increase in maternal tissue during the second trimester, and the fetus grows a great deal during the third trimester.
Weight gain varies, of course. A pregnant adolescent who is still growing should gain more weight than a mature woman of the same size. Underweight women should gain 28 to 40 pounds. Women of average weight should avoid excessive weight gain and try to stay within the 25- to 35-pound average gain. If the woman is pregnant with twins, then the recommended weight gain is 35 to 45 pounds. Overweight women can afford to gain less than the average woman, but not less than 15 pounds.
No one should lose weight during pregnancy, because it could cause nutrient deficiencies for both mother and infant. On average, a pregnant adult requires no additional calories during the first trimester of pregnancy and only an additional 300 calories a day during the second and third trimesters.