What are the nutritional recommendations for pregnant women?

Nutritional Recommendations for Pregnant Women

All pregnant women should take 400 µg/day of folic acid (or 5 mg/day if obese or diabetic) starting before conception, 30 mg/day of iron during the second and third trimesters, and consume an additional 300 kcal/day during the second and third trimesters while avoiding hypocaloric diets below 1,200 calories/day, which cause ketonemia linked to lower offspring intelligence. 1

Essential Supplementation Requirements

Folic Acid

• Begin 400 µg/day before conception and continue through at least the first trimester to prevent neural tube defects and congenital abnormalities 1
• Increase to 5 mg/day if obese or diabetic 1
• This is the single most critical supplement for preventing birth defects 2

Iron

• Administer 30 mg/day during the second and third trimesters to prevent maternal anemia and support increased blood volume 1
• Low-dose supplementation is necessary because most pregnant women cannot meet iron requirements from diet alone 3

Calcium

• Provide 1.0-1.5 g elemental calcium daily as calcium carbonate in divided doses of no more than 500 mg per dose 4
• This prevents preeclampsia in populations with low dietary calcium intake 4
• Calcium and iron-folic acid supplements can be taken together despite acute inhibitory effects on iron absorption, as clinical studies show minimal impact 4

Zinc

• Consider supplementation for women with low pre-pregnancy weight and low plasma zinc levels, as average intake (11 mg/day) falls below the RDA (15 mg/day) 1
• Supplementation leads to higher infant birth weight 4, 1

Vitamin D

• Ensure adequate intake through supplementation, particularly in populations at risk of deficiency 2
• Very few foods provide sufficient vitamin D to meet pregnancy requirements 3

Energy and Macronutrient Requirements

Energy Intake by Trimester

• First trimester: No additional calories unless the woman begins pregnancy with depleted body reserves 1
• Second and third trimesters: Add 300 kcal/day to support maternal blood volume expansion, breast and uterine growth, placental development, fetal growth, and amniotic fluid 4, 1
• Obese women with ample fat stores may require only 100 kcal/day above prepregnancy intake 4

Protein Requirements

• Consume 1.2 g/kg/day during early pregnancy (16 weeks) and 1.52 g/kg/day during late pregnancy (36 weeks) 1
• This represents a significant increase from older recommendations of 0.75 g/kg/day plus 10 g/day 4, 1

Meal Distribution

• Distribute carbohydrates throughout the day into three small-to-moderate meals and 2-4 snacks 1
• Include an evening snack to decrease overnight hypoglycemia and fasting ketosis 1
• This pattern is particularly important for insulin-treated women 1

Weight Gain Targets by Pre-Pregnancy BMI

• Underweight women (BMI <19.8): Gain up to 18 kg total 1
• Normal-weight women: Gain 1.4-2.3 kg in the first trimester and 0.5-0.9 kg/week during the second and third trimesters 4, 1
• Overweight women: Gain at less than 50% of the normal-weight rate 4, 1
• Obese women (BMI >30): Limit total weight gain to 5.0-9.1 kg 1

Critical Dietary Restrictions

Absolute Avoidances

• Completely avoid alcohol during pregnancy, as no amount is considered safe 1
• Avoid vitamin A in retinol form during the first 12 weeks due to teratogenic risk 1
• Avoid raw animal products and soft cheeses to prevent foodborne illness 1

Caffeine and Sweeteners

• Limit caffeine to no more than 200 mg per day 1
• FDA-approved nonnutritive sweeteners (saccharin, aspartame, acesulfame-K, and sucralose) appear safe but should be used in moderation 4, 1
• Saccharin can cross the placenta and remain in fetal tissues due to slow fetal clearance, though no evidence of ill effects exists 4

Critical Pitfalls to Avoid

Hypocaloric Diets

• Never prescribe diets below 1,200 calories/day, as they result in ketonemia and ketonuria associated with lower intelligence scores in offspring at ages 2-5 years 4, 1
• Even modest energy restriction (33% calorie reduction to 1,600-1,800 kcal/day) in obese women with gestational diabetes can reduce mean blood glucose without ketonuria 4
• More severe restriction (50% calorie reduction) increases ketonuria by twofold 4

Monitoring for Inadequate Intake

• Use daily food records, weekly weight checks, and ketone testing to ensure women are not under-eating to avoid insulin therapy 4, 1
• This monitoring prevents the dangerous practice of restricting calories to avoid medical intervention 1

Balanced Diet Composition

Food Emphasis

• Emphasize fruits, vegetables, legumes, whole grains, nuts, seeds, fish, and lean protein to provide adequate micronutrients naturally 1
• A balanced diet resulting in appropriate weight gain generally supplies all vitamins and minerals needed 4

Practical Reality

• Most pregnant women in the United States are at risk of inadequate intake of key nutrients from foods alone 5, 3
• No single food provides sufficient amounts of all 6 key nutrients (vitamins A and D, folate, calcium, iron, and omega-3 fatty acids) 3
• Seaweed provides 5 of 6 nutrients but would require intake of more than 5 cups daily 3
• Dietary supplements are necessary to meet vitamin D and iron targets, as well as omega-3 fatty acid targets for individuals who do not consume fish products 3

Special Populations

Post-Bariatric Surgery

• Require nutritional screening every trimester, including ferritin, folate, vitamin B12, calcium, vitamin D, and vitamin A levels 1
• Continue vitamin supplementation as recommended for bariatric patients with adaptations 4
• Pregnancy should be considered high-risk due to increased risk of preterm birth, shortened gestation, small-for-gestational-age birth, and gastrointestinal complications 4
• Monitor vitamin B12 levels every trimester in at-risk populations, as severe deficiency can occur in exclusively breastfed infants born to mothers who underwent gastric bypass 4, 1

Women with Diabetes

• Regular aerobic exercise (minimum three episodes per week, each >15 minutes) lowers fasting and postprandial glucose concentrations 4
• 2-4 weeks of regular exercise may be required before lowering of glycemia occurs 4

Supplement Quality Considerations

• Almost no US dietary supplements provide key nutrients in the doses needed for pregnant women without inducing excess intake 5
• Out of 20,547 dietary supplements (including 421 prenatal products), only 1 product (not a prenatal) contained target doses for all 6 key nutrients, but it costs approximately $200/month and requires 7 tablets per daily serving 5
• Herbal products lack standardization and vary in active ingredient content, posing risk to patients 6
• Patients should report all herbal supplement use to healthcare providers due to potential drug interactions 6