Nutrition and Pregnancy: Facts and Fictions
At no other time in a woman’s life is good nutrition more essential than during pregnancy. While the need for
At no other time in a woman’s life is good nutrition more essential than during pregnancy. While the need for calories increases only about 15 percent, the requirements for some nutrients more than doubles, and a woman needs to plan her diet carefully to meet these needs. The suggestions below outline how to take care of yourself in preparing to welcome your baby:
Upon learning she is pregnant, a woman should work with her doctor or other health professional providing prenatal care to design an eating program that supplies optimal nutrition for her and her baby. Any woman planning a pregnancy should also evaluate her eating habits. Even before trying to conceive, she should eat well to achieve ideal nutritional status as well as a healthy weight. Women who are too thin often have low-birth-weight babies, while those who are overweight have a greater risk of gestational diabetes and giving birth to an oversized baby. Infants who are either too small or too large at birth often suffer serious problems, including respiratory disorders.
During pregnancy, the recommended weight gain for a woman of average weight experiencing an average pregnancy is approximately 25 to 35 lb (11-16 kg). Women who are underweight at conception may need to gain as much as 40 lb (18 kg), however, and women who are overweight may be advised to gain no more than 15 to 25 lb (6.8-11 kg). Obese woman should not try to lose weight during pregnancy; to do so exposes her fetus to numerous hazards.
The pattern of weight gain is just as important as the amount gained. It is normal for most women to gain no weight during the first trimester. After that, a healthy woman at ideal weight before conceiving should gain an average of 1 lb (0.45 kg) a week; underweight women should gain slightly more each week; overweight women should gain more slowly.
Most women need to add approximately 300 calories to their daily diet to support normal fetal growth, especially during the last two trimesters. This is a relatively small amount, despite the saying about “eating for two.” A woman who doubles what she normally eats will certainly gain excessive weight. Appropriate foods that add up to 300 extra calories include 2 1/2 cups of low-fat milk; a sandwich made with 3 oz (85 g) of lean chicken; or an egg and two slices of toast.
Getting protein. A pregnant woman needs to consume an extra 25 g of protein daily — the amount found in 1 1/2 cups of milk (12 g of protein) and 2 oz (60 g) of cooked meat (14 g of protein). Because North Americans tend to eat more protein than necessary, no specific effort to increase protein consumption should be made during pregnancy. Some studies suggest that excessive protein may be detrimental to the fetus, causing delayed growth or premature birth.
When selecting protein-rich foods, include lean meats, poultry, and fish, which are also good sources of B vitamins and iron and other trace minerals. Other foods high in protein include: eggs. cheese, grains, and legumes.
Lacto-ovo vegetarians can obtain protein from milk and eggs; vegans, who eat only plant foods, should consult a dietitian on how to plan an adequate diet.
Getting calcium. A pregnant woman needs 1,000 mg of calcium a day. Because many North American women do not get enough calcium, it’s a good idea to increase consumption of calcium-rich foods before becoming pregnant. This is especially important for women under 30, whose bones are still increasing in density.
Dairy doses. Low-fat milk and dairy products are the best dietary sources of calcium; other good sources include fortified soy and rice beverages, tofu, canned sardines and salmon with the bones included, nuts and seeds, and leafy green vegetables. One cup of milk has about 300 mg of calcium per day — almost a third of the way toward the recommended 1,000 mg. One ounce (30 g) of cheddar cheese contains 204 mg, 1 oz (30 g) of low-fat mozzarella contains 207 mg, and 1/2 cup of yogurt contains about 230 mg.
Dairy alternatives. If you’re not a milk drinker, you can get about the same amount of calcium as a cup of milk from one cup of fortified soy or rice beverage, 2 cups of baked beans, 4 oz (115 g) of canned salmon, with the bones, 7 sardines, 3 cups of cooked broccoli, 2/3 cup of tofu, 3/4 cup of almonds, or 2 1/4 cups of soy beans. Calcium is also present in kale, Swiss chard, and other greens. If a doctor recommends calcium supplements, they should be consumed with meals to increase absorption and reduce intestinal upsets.
Getting iron. A woman’s iron requirement almost doubles during pregnancy, going from 18 mg to 27 mg daily. This is because the woman’s blood volume doubles and because the fetus must store enough iron to last through the first few months of life. Iron-rich foods include red meat, fish, poultry, enriched breads and cereals, legumes, eggs, dried fruits, and leafy green vegetables. However, the heme iron in animal products is absorbed more efficiently than the nonheme iron in plants and eggs. Absorption of nonheme iron can be increased by eating the iron-rich food together with one that is high in vitamin C, such as orange juice.
Even a well-balanced diet provides only about 12 mg to 15 mg of iron a day, and if a woman’s iron stores are low when pregnancy begins, she risks developing anemia. Most women need to take an iron supplement during pregnancy. These supplements are absorbed best if they are taken between meals with liquids other than coffee, tea, and milk, which decrease the absorption of iron.
Getting folate. Adequate folate, or folic acid, can help prevent birth defects, especially those involving the brain and spinal cord, such as spina bifida — a condition in which the spine does not form normally. It is estimated that 50 to 70 percent of such defects could be prevented if all women of childbearing age consumed folate. The Recommended Dietary Allowance (RDA) calls for 400 mcg (micrograms) of folate for women who are not pregnant; this increases to 600 mcg during pregnancy and then changes to 500 mcg during breast-feeding.
Many women, particularly those who have been taking birth control pills, have low levels of folate. Because the most critical period for folate consumption is during the first 4 to 6 weeks of pregnancy, when the fetal central nervous system is being formed, women planning to become pregnant are generally advised by their doctors to take a supplement before conceiving. Good dietary sources of folate:
1. green leafy vegetables
2. orange juice
3. lentils, peas and beans
6. fortified flour
Getting sodium. In the past, pregnant women were routinely advised to cut down on salt because it was thought to increase the risk of toxemia, a potentially life-threatening condition. There is no evidence, however, that salt restriction prevents or alleviates toxemia; on the contrary, a woman’s sodium requirement actually increases during pregnancy. In most cases, though, it is not necessary to consume additional salt.
About vitamin supplements. Experts agree that women should take folate and iron supplements during pregnancy, but there are differing views about whether other supplements are necessary. Many doctors believe that a balanced diet that includes a variety of foods in the recommended amounts will meet most needs, while others prescribe a multivitamin supplement as added insurance against deficiencies.
About alcohol. Women who are pregnant should abstain from alcohol consumption. Alcohol causes the most harm to a fetus during the first few weeks of a pregnancy, and the woman may not know that she has conceived. Studies show that women who have one to two drinks a day tend to have undersized babies. A greater danger is incurred by alcoholics during early pregnancy; these women have a high risk of giving birth to a baby with fetal alcohol syndrome, a constellation of congenital defects that may include mental deficiency, facial and heart malformations, an undersized head, and retarded growth. In addition, avoid: smoking and all drugs (unless prescribed by a doctor).
About artificial sweeteners. Controversy has swirled around the use of artificial sweeteners. Extensive studies on aspartame suggest that it is safe to use during pregnancy, unless the woman has phenylketonuria (PKU). Saccharin can cross the placenta, but there is no proof that it harms the fetus. Acesulfame-K and sucralose pass through the digestive tract and are excreted unchanged, and no toxic effect has been shown. Most experts believe that sweeteners used moderately are not harmful during pregnancy.
A recent study found an increased risk of spontaneous abortion and low birth weight in pregnant women who consumed more than 150 mg of caffeine per day. Some evidence suggests high levels of caffeine may delay conception. And yet other studies have failed to find any association between caffeine consumption and birth defects or premature birth. Since adverse effects on pregnancy outcomes have been linked to high caffeine intake, a position paper from the American Dietetic Association states that it would be prudent to limit caffeine intake to under 300 mg per day. One cup of filter drip coffee has about 200 mg of caffeine and 1 cup of black tea has about 100 mg.
About mercury. Mercury is an established environmental pollutant with known toxicity in humans. Pregnant women and women who may become pregnant should avoid large, long-lived fish, such as king mackerel, tilefish, shark, swordfish, and fresh tuna.
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