Question: I just found out I’m pregnant, and want to make sure I eat well. How much do I need to eat, and what kinds of foods are best? How much weight should I gain?
Answer: Eating a healthy, balanced diet during pregnancy helps to ensure proper fetal development, good maternal health, and appropriate weight gain. The amount each woman needs to eat during pregnancy will depend upon her activity level and pre-pregnancy weight; decisions regarding caloric intake and weight gain during pregnancy should be made in tandem with an obstetrician. In general, however, women who are of appropriate body weight before pregnancy should expect to gain 25–35 pounds by their due date . An increased energy intake of about 340–450 calories per day is generally sufficient to produce the desired weight gain . Note that pregnancy weight gain isn’t all — or even mostly — due to increased body fat. Rather, much of the weight comes from fetal mass, amniotic fluid, increased maternal blood volume, and the weight of the placenta. There is a moderate increase in body fat during a normal pregnancy. Excessive weight gain, however, increases body fat significantly. This puts the mother at increased risk of obesity post-pregnancy, as well as increased risk of a c-section, gestational diabetes, and preeclampsia .
While individuals may have specific dietary considerations or restrictions that should be discussed with an obstetrician, a healthy pregnancy diet looks very similar to a healthy diet at any other time. It should be varied and made up of mostly whole foods including fresh fruits and vegetables, lean sources of protein, whole grains, and healthy, plant-based fats. Women who experience significant morning sickness at any time during pregnancy and consequently find their diets quite limited should discuss their concerns with an obstetrician.
Nutritious foods aside, another important component of the pregnancy diet is supplementation with certain key vitamins and minerals. One of the easiest ways to achieve this is to take a prenatal vitamin. Prenatals are quite similar in composition to women’s daily multivitamins, though they’re quite a bit higher in some of the micronutrients — that is, vitamins and minerals — that are critical to a healthy pregnancy. For instance, prenatal vitamins contain significantly more iron than found in women’s daily multivitamins. Evidence suggests that 27–30 mg/day of iron is best during pregnancy, while non-pregnant women need only 18 mg/day . Iron is a key component of hemoglobin, the protein in red blood cells that binds to oxygen and helps deliver it to the tissues. Because blood volume increases significantly during pregnancy, necessitating the synthesis of large quantities of red blood cells, the added iron is of great importance. Another critical micronutrient is folic acid, a B-vitamin that has a number of roles in metabolism and the nervous system. Very early in pregnancy, sufficient stores of folic acid in the mother’s body help to prevent the birth defect spina bifida. Pregnant women should get at least 400-800 mcg (0.4-0.8 mg) of folic acid per day . Additional micronutrients of particular importance during pregnancy include calcium (1000–1300 mg/day ) and vitamin D in cases in which there is inadequate sun exposure . While it’s theoretically possible to get all the necessary vitamins and minerals from a balanced diet, it can be difficult to get sufficient quantities — particularly of folic acid and iron — to support a healthy pregnancy from food. The major utility of prenatal supplementation, then, is to act as a sort of insurance.
There is some interesting emerging research in the field of epigenetics — the study of the ways in which environment affects genes — that suggests a woman’s diet during pregnancy may help to determine her developing child’s tastes later in life . That is to say, a woman who eats a high-fat diet during pregnancy may be more likely to produce a child who particularly craves sugary and fatty foods. Further, a high-fat diet and subsequent maternal obesity during pregnancy could increase the likelihood that the offspring will be obese later in life . Still, when it comes to a healthy diet during pregnancy, the best attitude to take is one of moderation. It’s not reasonable to ignore nutrition completely, “eat for two,” and satisfy every craving with high-sugar, high-fat, low-nutrient fare. Neither is it reasonable, however, to worry about the nutritional content of every forkful; if nothing else, the stress of the latter isn’t healthy.
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- American College of Obstetrics and Gynecology. ACOG Committee Opinion number 315, September 2005. Obesity in pregnancy. Obstet Gynecol. 2005 Sep;106(3):671-5.
- Recommendations to prevent and control iron deficiency in the United States. Centers for Disease Control and Prevention. MMWR Recomm Rep. 1998 Apr 3;47(RR-3):1-29.
- American Academy of Pediatrics, American College of Obstetricians and Gynecologists. Guidelines for perinatal care. 5th ed. Elk Grove Village, Ill.: American Academy of Pediatrics, and Washington, D.C.: American College of Obstetricians and Gynecologists, 2002.
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- Wu et al. Parental obesity and overweight affect the body-fat accumulation in the offspring: the possible effect of a high-fat diet through epigenetic inheritance. Obes Rev. 2006 May;7(2):201-8.