Best Nutrition for Pregnancy
A balanced diet with adequate protein (1.2-1.52 g/kg/day depending on trimester), 400 µg/day folic acid supplementation, 30 mg/day iron in the second and third trimesters, appropriate weight gain based on pre-pregnancy BMI, and an additional 300 kcal/day after the first trimester forms the foundation of optimal pregnancy nutrition. 1, 2
Essential Supplementation
All pregnant women must take 400 µg/day of folic acid (or 5 mg/day if obese or diabetic) starting before conception and continuing through at least the first trimester to prevent neural tube defects and congenital abnormalities. 1, 3 This is non-negotiable regardless of dietary intake.
Iron supplementation of 30 mg/day is required during the second and third trimesters to prevent maternal anemia and support increased blood volume. 3, 2 While a balanced diet generally supplies most vitamins and minerals, prenatal supplements are commonly prescribed due to uncertainty about nutritional status. 3
Zinc supplementation should be considered for women with low pre-pregnancy weight and low plasma zinc levels, as the average intake (11 mg/day) falls short of the RDA (15 mg/day), and supplementation leads to higher infant birth weight. 3, 1
Protein Requirements by Trimester
Protein needs increase substantially as pregnancy progresses. The most recent evidence using the indicator amino acid oxidation method shows requirements of 1.2 g/kg/day during early pregnancy (16 weeks) and 1.52 g/kg/day during late pregnancy (36 weeks). 3 This is significantly higher than older recommendations of 0.75 g/kg/day plus 10 g/day. 3 Prioritize the higher values (1.2-1.52 g/kg/day) as they represent more recent and methodologically superior research. 3
Energy Requirements by Trimester
No additional calories are needed in the first trimester unless the woman begins pregnancy with depleted body reserves. 1, 2
Add 300 kcal/day during the second and third trimesters to support maternal blood volume expansion, breast and uterine growth, placental development, fetal growth, and amniotic fluid. 3, 2 Obese women with ample fat stores may require only 100 kcal/day above pre-pregnancy intake. 3
Weight Gain Targets by Pre-Pregnancy BMI
Underweight women (BMI <19.8): Gain up to 18 kg total, with 1.4-2.3 kg in the first trimester and 0.5-0.9 kg/week thereafter. 3, 4
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. 3, 4
Overweight women: Gain at less than 50% of the normal-weight rate (approximately 0.25-0.45 kg/week in the second and third trimesters). 4
Obese women (BMI >30): Limit total weight gain to 5.0-9.1 kg (some guidelines suggest 7 kg), with minimal gain during the second and third trimesters. 3, 4
Critical Dietary Restrictions
Completely avoid alcohol during pregnancy, as no amount is considered safe. 1, 2
Avoid vitamin A in retinol form during the first 12 weeks due to teratogenic risk; beta-carotene form is safe and preferred. 1
Avoid raw animal products and soft cheeses to prevent foodborne illness. 1
Limit caffeine to no more than 200 mg per day. 2
Meal Distribution and Timing
Distribute carbohydrates throughout the day into three small-to-moderate meals and 2-4 snacks. 3 An evening snack is usually necessary to decrease overnight hypoglycemia and fasting ketosis, particularly for insulin-treated women. 3
Carbohydrate is generally less well tolerated at breakfast than at other meals, so adjust morning intake accordingly. 3
Critical Pitfalls to Avoid
Never prescribe hypocaloric diets below 1,200 calories/day, as they result in ketonemia and ketonuria, which have been associated with lower intelligence scores in offspring at ages 2-5 years. 3, 1, 4 If calorie restriction is needed for obese women with gestational diabetes, limit to 33% calorie restriction (1,600-1,800 kcal/day) rather than 50% restriction. 3
Monitor for ketones using daily food records, weekly weight checks, and ketone testing to ensure women are not under-eating to avoid insulin therapy. 3
Do not use "no concentrated sweets" or "no sugar added" diets, as there is no evidence supporting these restrictions. 3
Balanced Diet Composition
Emphasize fruits, vegetables, legumes, whole grains, nuts, seeds, fish, and lean protein to provide adequate micronutrients naturally. 2 Food is the optimal vehicle for nutrient intake. 3
FDA-approved nonnutritive sweeteners (saccharin, aspartame, acesulfame-K, and sucralose) are safe during pregnancy when used in moderation. 3
Special Populations
Women post-bariatric surgery require nutritional screening every trimester, including ferritin, folate, vitamin B12, calcium, vitamin D, and vitamin A levels, with supplementation adjusted accordingly. 1
Vitamin B12 levels should be monitored every trimester with supplementation adjusted to maintain normal serum concentrations in at-risk populations. 1