Typically, a pregnant woman only needs to start consuming more calories after the first trimester, because early in pregnancy, the developing fetus is comparatively small in relation to the mother’s body mass. In general, in the second and third trimesters, pregnant women need between 2,200 and 2,900 total calories a day; the exact number depends on prepregnancy weight and the mother’s activity level. Women should increase their caloric intake gradually using nutrient-dense foods—ideally to meet increased energy demands they should eat on average an extra 340 calories per day in the second trimester and an extra 450 kcal per day in the third trimester. (Underweight women need more calories since they should gain more weight; overweight women need fewer. Physically active women require more calories to offset expenditure.)

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One excellent resource for pregnancy meal planning is the Health & Nutrition Information for Pregnant & Breastfeeding Women on the United States Department of Agriculture (USDA) ChooseMyPlate.org website, which provides a personalized daily food plan based on age, height, weight, physical activity level, and stage of pregnancy or breastfeeding status. That all said, a better gauge of appropriate intake is to monitor weight gain during pregnancy than to count daily calories. (INFOGRAPHIC 17.5)

Question 17.2

Pregnant women need more calories to support their growing baby and they need more nutrients for themselves, too, all of which are best supplied through a wide variety of nutrient-dense foods. That’s because all energy and nutrient needs for a baby’s growth and development come from what the mother eats. Even if she eats enough calories, a woman who does not consume adequate nutrients during pregnancy—or who consumes excess amounts—can put her baby at risk for birth defects and other anomalies, particularly if these discrepancies occur during periods of intense or accelerated fetal development known as critical periods. Critical periods are genetically determined pathways that direct the development of specific cell types, organs, and tissues. Disruption of growth or development during a critical period (from nutritional problem or toxic substance) may be irreversible.

Ultimately, pregnant women need only 15% more total calories than nonpregnant women, but about 50% more of some nutrients such as protein, folate, zinc, iodine, and iron. Pregnant women can meet most of their nutritional requirements through food; in fact, the only nutrient for which a supplement is universally recommended is iron. However, prenatal multivitamin-mineral supplements are sometimes recommended for women who do not consume an adequate diet or those who have high-risk pregnancies. Women who are vegans should also supplement with additional vitamin D, iron, and vitamin B₁₂. When choosing supplements, women should follow the advice of their doctor or midwife and not buy products that contain more than the recommended intake of any nutrient.

Folate (the synthetic form of which is called folic acid), a water-soluble B vitamin, is one of the key nutrients mothers-to-be need before and during pregnancy, as it is crucial for the development of new cells. Folate deficiency is associated with fetal growth problems, birth defects, schizophrenia, and autism; in addition, women who don’t get enough folate during the first 12 weeks of pregnancy are up to 70% more likely to give birth to babies with neural tube defects, such as spina bifida.

The U.S. Centers for Disease Control and Prevention (CDC) recommends that all women between the ages of 15 and 45 years—even if they are not pregnant—consume a daily dose of 400 micrograms of folic acid in a multivitamin or the equivalent through folate-rich foods. This recommendation applies to all women of child-bearing age because half of U.S. pregnancies are unplanned, and birth defects from folate deficiency develop as early as three to four weeks into pregnancy, before most women even know they are pregnant. During pregnancy, women should consume the equivalent of 600 micrograms of folate daily from foods or supplements. To help women meet these requirements, in 1998, the U.S. Food and Drug Administration began requiring food manufacturers to add folic acid to common grain products such as breads, cereals, flours, and pastas.

Another nutrient of particular concern during pregnancy is vitamin A, but expectant women need to be careful about how much of it they consume, because although too little vitamin A can cause developmental problems, too much can also cause birth defects such as facial and heart deformities. Women can thus keep the risk of vitamin A toxicity low by meeting their needs through the consumption of bright orange, deep yellow, and light red vegetables and fruits that are rich in the vitamin A precursor, beta carotene. See Chapter 10 for more information on food sources of vitamin A.

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The Institute of Medicine recommends that pregnant women between the ages of 19 and 50 years consume 770 micrograms of vitamin A per day, not exceed the Tolerable Upper Intake Level of 3,000 micrograms per day, and stop taking medications that contain vitamin A. The precursor to vitamin A, beta-carotene, however, does not seem to have the same potential adverse effects.

Iron deficiency is the most common deficiency in pregnant women. Iron is used to make hemoglobin, the molecule that transports oxygen through blood, and pregnant women vastly increase their production of hemoglobin to supply oxygen to their fetuses and to help build a fetal blood supply. The daily recommended intake of iron for pregnant women is 27 milligrams per day, compared with only 15 to 18 milligrams for nonpregnant women, yet national surveys have reported that pregnant women generally consume only 15 milligrams per day—just over half of the recommended amount. To ensure adequate iron intake, women should consume fortified cereals and green leafy vegetables, both good sources of non-heme iron; particularly if consumed with vitamin C-rich foods such as citrus fruits. Red meats are a good source of readily absorbable heme iron.

It is difficult for women to meet their increased iron needs from food alone, so supplements of 30 milligrams of iron are typically recommended during the second and third trimesters. Women who don’t take supplements are at an increased risk of suffering from iron-deficiency anemia and are also at risk for giving birth to low-birth-weight babies who become iron-deficient in their first year of life.

Many other nutrients are important for a healthy pregnancy. There’s calcium, which is crucial for the formation of healthy bones, and although absorption is enhanced during pregnancy, the recommendation for pregnant women is still 1,000 milligrams daily. Vitamin D helps to incorporate calcium into bones and also appears to play a role in programming genes in ways that could reduce the risk of chronic diseases; pregnant women should consume 600 IUs (15 micrograms) daily. Iodine is required for normal brain development and growth and recent studies indicate that approximately one-third of pregnant women in the United States are marginally deficient in iodine. The Institute of Medicine recommends 220 micrograms per day for pregnant women.

The omega-3 fatty acids, such as EPA and DHA, are critical for the development of the fetal brain. During pregnancy, the placenta transfers nutrients from the mother to the fetus. The amount of omega-3 fatty acids in the fetus is correlated with the amount consumed by the mother, underscoring the importance of adequate nutrition. Although the U.S. government has not made official recommendations about omega-3 intake during pregnancy, several organizations recommend that pregnant women consume 300 milligrams of DHA daily—yet most women do not meet this recommendation. Cold-water fish are a great source of these omega-3 fatty acids and thus recent recommendations encourage pregnant women to consume 8 to 12 ounces of fish each week. But because of concerns about mercury contamination in some types of fish, pregnant women are told to choose low-mercury fish and avoid fish that have potentially high levels of mercury, such as shark, swordfish, king mackerel, and tilefish. Women who consume too much mercury during pregnancy are more likely to give birth to babies with central nervous system defects and slow cognitive development. However, pregnant women may safely enjoy salmon, cod, shrimp, sardines, anchovies, and trout, and are advised to limit albacore tuna and tuna steak to six ounces a week.