Nutrition in pregnancy can affect maternal health and infant size and well-being. Pregnant women should have nutrition counseling early in prenatal care and access to supplementary food programs if necessary. Counseling should stress abstention from alcohol, smoking, and recreational drugs. Caffeine and artificial sweeteners should be used only in small amounts. "Empty calories" should be avoided, and the diet should contain the following foods: protein foods of animal and vegetable origin, milk and milk products, whole-grain cereals and breads, and fruits and vegetables—especially green leafy vegetables.
Recommendations regarding weight gain in pregnancy should be based on maternal BMI preconceptionally or at the first prenatal visit. According to the National Academy of Medicine guidelines, total weight gain should be 25–35 lbs (11.3–15.9 kg) for normal weight women (BMI of 18.5–24.9) and 15–25 lbs (6.8–11.3 kg) for overweight women. For obese women (BMI of 30 or greater), weight gain should be limited to 11–20 lbs (5.0–9.1 kg). Excessive maternal weight gain has been associated with increased birth weight as well as postpartum retention of weight. Not gaining weight in pregnancy, conversely, has been associated with low birth weight. Nutrition counseling must be tailored to the individual patient.
Rigid salt restriction is not necessary. While consumption of highly salted snack foods and prepared foods is not desirable, 2–3 g/day of sodium is permissible. The increased calcium needs of pregnancy (1200 mg/day) can be met with milk, milk products, green vegetables, soybean products, corn tortillas, and calcium carbonate supplements.
The increased need for iron and folic acid should be met with foods as well as vitamin and mineral supplements. (See Anemia section.) Megavitamins should not be taken in pregnancy, as they may cause fetal malformation or disturbed metabolism. However, a balanced prenatal supplement containing 30–60 mg of elemental iron, 0.4 mg of folate, and the recommended daily allowances of various vitamins and minerals is widely used in the United States and is probably beneficial to many women with marginal diets. There is evidence that periconceptional folic acid supplements can decrease the risk of neural tube defects in the fetus. For this reason, the United States Public Health Service recommends the consumption of 0.4 mg of folic acid per day for all pregnant and reproductive age women. Women with a prior pregnancy complicated by neural tube defect may require higher supplemental doses as determined by their providers. Lactovegetarians and ovolactovegetarians do well in pregnancy; vegetarian women who eat neither eggs nor milk products should have their diets assessed for adequate calories and protein and should take oral vitamin B12 and vitamin D supplements during pregnancy and lactation.
American College of Obstetricians and Gynecologists. ACOG Committee Opinion No. 548: Weight gain during pregnancy. Obstet Gynecol. 2013;121:210. [Reaffirmed 2020]
American College of Obstetricians and Gynecologists' Committee on Practice Bulletins-Obstetrics. Obesity in Pregnancy: ACOG Practice Bulletin, no. 230. Obstet Gynecol. 2021;137:e128.