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Eating nutritiously before conception and throughout pregnancy is essential for your baby’s health. Carbohydrates, protein and fat fuel a healthy pregnancy, and eating a variety of nutritious foods, including whole grains, fruits, vegetables, low fat dairy and lean protein, helps provide the vitamins and minerals needed for the healthy development of your baby. Diets that restrict calories and wholesome carbohydrates are not appropriate for women who are pregnant.
Skimping on calories and carbohydrates can pose serious risks for a growing baby. Women who don’t gain enough weight have a greater chance of having low birth weight babies, and these babies have a greater chance of health and developmental problems. Gaining too much weight is also not good, since it could make delivery, as well as losing weight after pregnancy, more difficult.
The appropriate amount of weight gain depends on a woman’s prepregnancy weight, or more specifically, her body mass index, or BMI. The Institute of Medicine recommends the following:1
| Prepregnancy Weight | Prepregnancy BMI | Weight Gain (in pounds) |
|---|---|---|
| Underweight | <19.8 | 28-40 |
| Normal | 19.8-26 | 25-35 |
| Overweight | >26-29 | 15-25 |
| Obese | >29 | 15 |
Pregnancy requires an average of 300 extra calories a day.2 These extra calories are especially important during the second and third trimester of pregnancy. Adding a nutritious mid-morning or mid-afternoon snack can help meet energy needs.
Some nutritious 300-calorie combinations
Still, there may be days when a mom-to-be does not need more food, particularly early in pregnancy and when morning sickness occurs, and there may be days when she is especially hungry and should eat more food. What’s important is to eat nutritiously throughout pregnancy.
Low carbohydrate, high protein diets are not appropriate during pregnancy. The Recommended Dietary Allowance (RDA) for carbohydrates during pregnancy is 175 grams per day.3 Getting this amount of carbohydrates is important to help prevent hypoglycemia, or low blood sugar, during pregnancy. The RDA is higher than the amount of carbohydrates recommended during the weight loss or maintenance phases of low carbohydrate diet programs.
Low carbohydrate diets can also make it harder to get some vitamins and minerals essential for the mother and her developing baby. Folic acid and calcium are two such nutrients.
Folic acidPregnancy increases the need for folic acid, a vitamin that helps produce red blood cells and is needed to prevent birth defects that can occur in the first few weeks of pregnancy. In the growing fetus, new cells are constantly needed as the body increases in size. Folate (or folic acid) is also needed for brain growth and development of the nervous system. Because of its vital importance in preventing birth defects during pregnancy, the Food and Drug Administration requires that folic acid be added to flour, bread and grain products, like rice and noodles.
In addition to enriched bread and grains, many fortified breakfast cereals contain folic acid. Folate is found naturally in legumes (beans, peas and lentils), leafy green vegetables, and some fruits. Since most of these foods are restricted on low carbohydrate diets, women who “count carbs” will likely not get enough of this important nutrient in their diets. That’s a good reason to include carbohydrates in your diet, and to choose these foods wisely. To reduce the risk of neural tube defects in women capable of becoming pregnant, it is recommended that all women of childbearing age get 400 micrograms of folic acid daily from fortified foods and supplements, in addition to foods containing folate.4
CalciumCalcium is another nutrient that is important for both the mom-to-be and her baby. A good diet during pregnancy should include enough calcium to help build and maintain strong bones and teeth. It is best for the developing baby to obtain the calcium it needs from the mother’s diet. If the mother’s diet is inadequate, the developing baby gets its calcium from the mother’s bones. To compensate for the baby’s calcium withdrawal, pregnant women absorb more calcium from foods than women who aren’t pregnant. Still, a steady supply of dietary calcium is needed to help maintain the mother’s bone calcium stores.
Milk, yogurt and calcium-fortified juices are some of the best sources of calcium. Yet, these foods are often limited on low carbohydrate diets. For people who “count carbs,” cheese is also an excellent source of calcium; tofu (made with calcium), broccoli and almonds also contain some calcium. However, restricting most dairy foods and calcium-fortified juices because of their carbohydrate content means there are fewer calcium-rich foods to choose from to meet dietary requirements.
Since calcium absorption from foods increases during pregnancy, calcium requirements are the same for pregnant and nonpregnant women. It is recommended that women ages 19-50 get 1000 milligrams of calcium a day; teens ages 14-18 should consume 1300 milligrams of calcium daily. 6 Eating at least 3 servings from the Milk, Yogurt and Cheese food group daily can help meet these recommendations. One serving equals 1 cup milk, 8 ounces yogurt, or 1½ ounces hard cheese. The average calcium intake of American women and teens falls far short of the recommendations.7
Research on high protein, low carbohydrate diets and pregnancySome animal and human research has shown that high protein, low carbohydrate diets may have adverse effects on the fetus, as well as the offspring later in life. In rat studies, maternal dietary carbohydrate is essential for fetal growth and survival of the newborns.8 Even with a diet that is adequate in calories and protein, restriction of dietary glucose lowers tissue glycogen reserves (i.e., the stored form of glucose) and interferes with the normal development of the glucose-regulating system – the system that uses insulin and other hormones to control blood glucose levels and insures that glucose is delivered to all the cells that need it after birth.8
In research presented at a 2004 conference of the European Society of Human Reproduction and Embryology, a moderately high protein diet (25% of calories) adversely affected genetic imprinting in mice embryos, embryo implantation in the womb and subsequent fetal development. This may be due to the high ammonium levels in the reproductive tract that result from eating a high protein diet. Whether these findings in animals apply to humans is unknown, however the researchers advised women trying to conceive to limit their protein intake to less than 20% of total calories.9
In a British study on humans, pregnant mothers who ate a high meat/fish diet in late pregnancy were shown to have increased cortisol levels.10 This is a concern since in animals, high fetal exposure to cortisol may lead to elevated blood pressure in the offspring later in life. The researchers suggested that high maternal cortisol levels may expose the fetus to excess cortisol and program lifelong excess secretion of cortisol in the offspring. Additional research, with more sensitive measures of food intake, is needed.
In gestational diabetes—when a pregnant woman gets diabetes, but didn’t have it before pregnancy—the top priorities are to promote optimal growth and development of the fetus, normalize blood glucose levels and prevent excessive maternal weight gain.11 In a study investigating the relationship between maternal diet composition and newborn birth weight, a higher carbohydrate diet was linked to a lower occurrence of large birth weight babies.11 Having a large birth weight baby can make delivery more difficult. There were no large birth weight infants among women who consumed over 210 grams of carbohydrates a day. It was suggested that to improve insulin sensitivity in women with gestational diabetes, a high carbohydrate diet, that is also low in fat to limit daily calories, is recommended.
In addition, spreading out carbohydrates throughout the day and using carbohydrates with a low glycemic index—such as most vegetables, fruits, legumes, dairy products and whole grains—can help limit the rise in blood sugar after eating a meal.11 Here again, the idea is not to restrict carbohydrates in the diet, but to choose them wisely.