The Essential Guide to Key Nutrients for Fetal Development

The key nutrients for fetal development are folate (folic acid), iron, iodine, choline, the omega-3 fat DHA, vitamin D, calcium and vitamin B12, plus enough protein and calories from a varied diet. Most pregnant people need more of several of these than they did before pregnancy, so U.S. guidelines pair a healthy eating pattern with a daily prenatal vitamin chosen with your prenatal care provider. Food safety matters too: limit high-mercury fish, avoid alcohol and foods linked to Listeria, and keep caffeine moderate.

Evidence grade: Strong. The intake targets in this article are established NIH/National Academies reference values, and the folic acid advice is a USPSTF grade A recommendation based on a systematic review of human studies.

Why Pregnancy Changes Your Nutrient Needs

A growing baby, placenta and expanding blood supply raise the Recommended Dietary Allowance (RDA) for several nutrients. The 2020-2025 Dietary Guidelines for Americans recommend following a healthy eating pattern through pregnancy and note that a daily prenatal vitamin and mineral supplement may be especially important for meeting folate/folic acid, iron, iodine and vitamin D needs [9].

Needs differ from person to person, so treat every number below as a starting point for a conversation with your prenatal care provider.

Pregnancy Nutrient Targets at a Glance

Sources: NIH ODS [1, 4, 5, 6, 7, 8], USPSTF [2], FDA/EPA [10]. DFE = dietary folate equivalents; AI = Adequate Intake.

Folate and Folic Acid: Start Before Pregnancy

Folate is a B vitamin your body uses to make DNA and new cells. Folic acid is the form used in supplements and fortified foods. The RDA for folate rises from 400 mcg DFE to 600 mcg DFE during pregnancy and is 500 mcg DFE while breastfeeding [1].

The U.S. Preventive Services Task Force (USPSTF) recommends that all persons who plan to or could become pregnant take a daily supplement containing 0.4 to 0.8 mg (400 to 800 mcg) of folic acid. It advises starting at least 1 month before conception and continuing through the first 2 to 3 months of pregnancy; this is a grade A recommendation [2]. CDC similarly advises anyone who could become pregnant to get 400 mcg of folic acid every day [3].

According to CDC and the USPSTF, this advice exists to lower the risk of neural tube defects, serious birth defects of the brain and spine that develop in the first weeks of pregnancy, often before a person knows they are pregnant [2, 3]. CDC notes that folic acid is the only form of folate shown in studies to help prevent them [3].

Folate-rich foods include beans, spinach and other dark leafy greens, asparagus, avocado, oranges and fortified breakfast cereals [1].

Iron for a Growing Blood Supply

Iron helps make hemoglobin, the protein that carries oxygen in red blood cells. The iron RDA jumps from 18 mg to 27 mg a day in pregnancy, then falls to 9 mg while breastfeeding for adults [4]. The Dietary Guidelines note that iron deficiency affects about 1 in 10 pregnant women and about 1 in 4 during the third trimester [9].

Heme iron in lean meat, poultry and seafood is absorbed more readily than the non-heme iron in beans, peas, lentils and dark-green vegetables [9]. Vitamin C, and eating meat, poultry or seafood in the same meal, can improve absorption of iron from plant foods [4]. ACOG recommends low-dose iron supplementation starting in the first trimester and screening for low iron during pregnancy, so your provider may check your levels and adjust your dose [4]. More on iron and energy.

Iodine and Choline: The Two Most Often Missed

Iodine

Iodine is needed to make thyroid hormones, which support normal fetal brain development. The RDA rises from 150 mcg to 220 mcg in pregnancy and 290 mcg while breastfeeding [5]. The American Thyroid Association recommends that people who are planning a pregnancy, pregnant or breastfeeding take a supplement with 150 mcg of iodine a day as potassium iodide, yet NIH notes that some, but not all, prenatal supplements contain iodine [5]. Check the label of yours. Dairy, eggs, seafood and iodized salt are the main food sources; sea salt that is not iodized supplies almost none [5].

Choline

Choline is used to build cell membranes and the neurotransmitter acetylcholine. The Adequate Intake is 450 mg a day in pregnancy and 550 mg while breastfeeding [6]. NIH reports that roughly 90% to 95% of pregnant women eat less than this amount, and that prenatal supplements typically contain little if any choline [6]. One large hard-boiled egg supplies about 147 mg [6], and meat, fish, poultry and dairy are other main sources [6].

DHA and Seafood: Choose Lower-Mercury Fish

Fish supplies the omega-3 fats DHA and EPA, along with iron, iodine and choline, nutrients FDA and EPA describe as supporting a child's brain development [10]. Their joint advice for people who are pregnant or breastfeeding is 8 to 12 ounces of a variety of lower-mercury fish each week, which works out to 2 to 3 servings of 4 ounces from the "Best Choices" list [10].

• Best Choices include: salmon, sardines, anchovies, shrimp, cod, catfish, Atlantic mackerel, tilapia, trout and canned light tuna [10].
• Choices to avoid (highest mercury): king mackerel, marlin, orange roughy, shark, swordfish, tilefish from the Gulf of Mexico and bigeye tuna [10].

If you do not eat fish, ask your provider about DHA. Our overview of omega-3 fatty acids explains the difference between DHA, EPA and plant ALA.

Vitamin D, Calcium and Vitamin B12

Vitamin D promotes calcium absorption in the gut and supports normal bone [7]. The RDA is 600 IU (15 mcg) a day during pregnancy and breastfeeding, the same as for other adults [7]. Fatty fish, egg yolks and fortified foods such as milk provide some [7], and the Dietary Guidelines name vitamin D among the nutrients a prenatal supplement may help cover [9]. Calcium-rich dairy foods or calcium-fortified alternatives are part of the healthy eating pattern the Dietary Guidelines recommend in pregnancy [9].

Vitamin B12 is needed for healthy red blood cells and nerve function. The RDA rises slightly to 2.6 mcg in pregnancy and 2.8 mcg while breastfeeding [8]. B12 is found naturally only in animal foods, so the Dietary Guidelines advise people following a vegetarian or vegan pattern to talk with their provider about iron, B12, choline, zinc, iodine and EPA/DHA [9]. See nutrients that can be missing in vegan diets.

How Many Extra Calories Do You Need?

"Eating for two" overstates it. The Dietary Guidelines estimate that, for someone who started pregnancy at a healthy weight, calorie needs do not increase in the first trimester, then rise by about 340 calories a day in the second trimester and about 452 a day in the third [9]. Spend those calories on nutrient-dense foods rather than extra sweets. Follow your provider's guidance, since recommended weight gain depends on pre-pregnancy weight [9].

Eating Safely During Pregnancy

Foods linked to foodborne illness

Pregnancy changes the immune system, and some harmful bacteria can cross the placenta, so FDA advises pregnant people to avoid [11]:

• Raw or undercooked meat, poultry, eggs and foods made with raw eggs (some homemade dressings, cookie dough and eggnog).
• Raw fish, partially cooked seafood, raw shellfish and refrigerated smoked seafood.
• Unpasteurized (raw) milk and foods made from it, and queso fresco-type cheeses.
• Hot dogs, deli meats, fermented or dry sausages and smoked fish unless reheated until steaming hot.
• Deli-made salads such as ham, chicken or seafood salad, refrigerated pâtés, raw sprouts and unpasteurized juices.

Alcohol

The Dietary Guidelines list women who are pregnant among adults who should not drink alcohol [9].

Caffeine

ACOG's committee opinion on caffeine describes moderate consumption as less than 200 mg a day during pregnancy [12]. Tea, soda, energy drinks and chocolate count toward the total.

Safety and Interactions

• Folic acid: the upper limit for adults is 1,000 mcg a day from supplements and fortified foods combined, unless your clinician prescribes more [1]. High folic acid intake can mask a vitamin B12 deficiency, so B12 status matters too [1].
• Iron: the upper limit is 45 mg a day for adults, including during pregnancy [4]. Iron supplements can cause constipation and nausea, and they can interact with medicines such as levothyroxine and levodopa; talk to your doctor or pharmacist about timing if you take either [4].
• Iodine: more is not better. Some iodine-only supplements exceed the upper limit [5]. Talk to your doctor if you take antithyroid medicines or ACE inhibitors, which can interact with iodine supplements [5].
• Herbal products: check every herbal supplement and tea with your prenatal care provider first.

When you compare prenatal vitamins with your provider, check for 400 to 800 mcg of folic acid [2] and 150 mcg of iodine [5], and remember that most contain little if any choline [6]. Avoid stacking several products that contain the same nutrients.

Frequently Asked Questions

How much folic acid should I take before pregnancy?

CDC advises 400 mcg of folic acid every day for anyone who could become pregnant, and the USPSTF recommends 400 to 800 mcg daily, starting at least 1 month before conception [2, 3]. If you had a previous pregnancy affected by a neural tube defect, talk to your doctor, because higher doses are recommended [3].

Can I eat fish while pregnant?

Yes. FDA and EPA recommend 8 to 12 ounces a week of a variety of lower-mercury fish, such as salmon, sardines, shrimp and cod, and avoiding the highest-mercury fish, including swordfish, shark, king mackerel and bigeye tuna [10]. Avoid raw fish and refrigerated smoked seafood unless it is cooked [11].

How much caffeine is safe during pregnancy?

ACOG considers less than 200 mg a day moderate during pregnancy [12]. Count coffee, tea, soda, energy drinks and chocolate, and ask your provider whether a lower amount is right for you.

Do I really need to eat for two?

No. Calorie needs generally do not rise in the first trimester and increase by about 340 and 452 calories a day in the second and third trimesters for someone who began pregnancy at a healthy weight [9]. Once your baby arrives, our breastfeeding diet guide covers how needs change again.

Sources

1. NIH Office of Dietary Supplements. Folate: Fact Sheet for Health Professionals.
2. US Preventive Services Task Force. Folic Acid Supplementation to Prevent Neural Tube Defects: Preventive Medication. Final Recommendation Statement. 2023.
3. Centers for Disease Control and Prevention. About Folic Acid.
4. NIH Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals.
5. NIH Office of Dietary Supplements. Iodine: Fact Sheet for Health Professionals.
6. NIH Office of Dietary Supplements. Choline: Fact Sheet for Health Professionals.
7. NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals.
8. NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals.
9. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. Chapter 5 and Appendix 2. 2020.
10. U.S. Food and Drug Administration and U.S. Environmental Protection Agency. Advice about Eating Fish.
11. U.S. Food and Drug Administration. People at Risk of Foodborne Illness.
12. American College of Obstetricians and Gynecologists. Committee Opinion No. 462: Moderate Caffeine Consumption During Pregnancy. 2010 (reaffirmed).

Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.

Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: October 17, 2026 · How OPA researches and writes