First Trimester Nutrition Guide: Weeks 1 to 13

The first trimester is when most of the foundational development happens. The neural tube closes. The heart begins to beat. Major organ systems form. And most of this happens in the first eight weeks, often before a pregnancy is even confirmed.

Nutritionally, the first trimester is less about eating more and more about eating right. Calorie needs don't increase significantly in the first trimester, according to ACOG. What increases is the importance of getting specific nutrients consistently, often at a point when nausea makes eating consistently harder than usual.

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The Nutrients That Matter Most in the First Trimester

Folate

Folate is the most critical first trimester nutrient, and its work begins before most women know they're pregnant. The neural tube, which becomes the brain and spinal cord, closes by week 6. Neural tube defects develop in this window.

The CDC recommends 600 mcg of folic acid per day during pregnancy. Because so much depends on folate intake before and immediately after conception, ACOG advises women who might become pregnant to start taking a prenatal vitamin with at least 400 mcg of folic acid before conception.

Food sources of folate include lentils, spinach, black beans, asparagus, avocado, broccoli, and fortified cereals. Getting enough from food alone is difficult, which is why a prenatal vitamin is important. For the full picture, see our folate guide.

Choline

Choline plays a similar role to folate in neural tube formation, and it's critical for early brain development. ACOG recommends 450 mg per day during pregnancy. Yet fewer than 10% of pregnant women in the US reach this amount, according to survey data from the InfantRisk Center at Texas Tech University Health Sciences Center and most prenatal vitamins contain little to none.

The best food sources are egg yolks (around 147 mg each), chicken, beef, fish, soybeans, and kidney beans. Two eggs a day covers about 65% of the daily target. For the full guide, see our choline article.

Iron

Iron needs increase significantly during pregnancy because blood volume expands to support the fetus. The NIH recommends 27 mg of iron per day during pregnancy, up from 18 mg for non-pregnant women. Deficiency can cause anemia, which leads to fatigue and increases risk of preterm birth.

The first trimester is an important time to establish consistent iron intake. Many women experience significant fatigue in these weeks already, and anemia compounds it. Iron-rich foods include lean meat, poultry, lentils, spinach, and fortified cereals. Pairing iron with vitamin C improves absorption. See our complete iron guide.

Vitamin B6

Vitamin B6 is relevant in the first trimester specifically because of nausea. It's one of the few interventions with consistent research support for reducing morning sickness severity, and it's the basis for Diclegis (a common prescription for nausea in pregnancy) when combined with doxylamine. If nausea is affecting your ability to eat, B6 is worth discussing with your provider.

Iodine

Iodine supports thyroid function in the mother and is essential for fetal brain development. The recommendation during pregnancy is 220 mcg per day, according to ACOG. Many prenatal vitamins now include iodine, but it's worth checking your specific brand.

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The Challenge: Nausea

About 70 to 80% of pregnant women experience nausea in the first trimester, and for many, it significantly limits what they can eat. When nausea is bad, the goal shifts from optimal nutrition to maintaining adequate intake of what's tolerable.

A few principles that tend to help:

Eat before you're hungry. An empty stomach often makes nausea worse. Small, frequent meals or snacks throughout the day maintain blood sugar and reduce acid buildup.

Cold or room-temperature foods. Hot foods have stronger aromas, which can trigger nausea. Cold foods or foods at room temperature are often better tolerated.

Protein in the morning. Starting the day with some protein eggs, nut butter, Greek yogurt can help stabilize blood sugar before nausea sets in.

Ginger. Research supports ginger as an effective remedy for nausea. Ginger tea, ginger chews, or fresh ginger in food are all options. For more strategies, see our nausea guide.

If nausea is severe enough that you can't keep food or liquids down, contact your healthcare provider. Hyperemesis gravidarum (severe pregnancy nausea and vomiting) requires medical attention.

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Calorie Needs in the First Trimester

First trimester calorie needs are generally the same as pre-pregnancy, according to ACOG. You don't need to eat significantly more. What matters is that what you do eat is nutrient-dense.

If nausea is making it hard to eat, focus on what you can tolerate. A week of bland foods while nausea peaks isn't going to cause lasting harm. Getting folate, iron, and choline consistently matters more than hitting specific calorie targets.

The increase comes in the second trimester (around 340 extra calories per day, per ACOG).

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What to Avoid in the First Trimester

The first trimester is when food safety matters most, because the fetus is most vulnerable to exposure to bacteria and toxins during the period of rapid organ formation. This includes:

• Raw or undercooked meat, fish, and eggs
• High-mercury fish (shark, swordfish, king mackerel, bigeye tuna)
• Raw sushi and sashimi
• Cold deli meats and refrigerated smoked fish (Listeria risk)
• Unpasteurized dairy and soft cheeses
• Alcohol (no safe amount in pregnancy, per ACOG)

For the complete list and the reasoning behind each restriction, see our foods to avoid guide.

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Your Prenatal Vitamin

A prenatal vitamin taken consistently is one of the most important things you can do in the first trimester. Look for one that includes at least 400 mcg of folic acid, 27 mg of iron, 220 mcg of iodine, 200 mg of DHA, and some vitamin D.

One gap to be aware of: most prenatal vitamins contain little to no choline. Choline is difficult to include in standard capsule form. This is a known issue that ACOG and researchers have flagged, and it means dietary sources of choline matter even if you're taking a prenatal vitamin.

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How PregnantWise Supports the First Trimester

PregnantWise tracks all of the key first trimester nutrients folate, choline, iron, DHA, vitamin B6, iodine with daily goals that reflect the specific recommendations for pregnancy. When nausea limits what you're eating, you can see at a glance where the gaps are and which foods to prioritize when you're feeling better.

The partner dashboard is particularly relevant in the first trimester. Partners can manage shopping lists, track supplements, and understand what's going on nutritionally even during weeks when the pregnant person is too nauseous to manage much of this themselves.

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Frequently Asked Questions

When should I start taking a prenatal vitamin?

Ideally before you're pregnant. Folate is most critical in the first four to eight weeks, often before pregnancy is confirmed. ACOG recommends starting a prenatal vitamin at least one month before conception if possible.

Is it normal for weight to be lost in the first trimester because of nausea?

Some women lose a small amount of weight in the first trimester due to nausea and reduced appetite. This is generally not concerning as long as weight loss is modest. If you're losing significant weight or can't keep fluids down, contact your provider.

Do I need to eat more food in the first trimester?

No, calorie needs in the first trimester are generally the same as before pregnancy. The increase comes in the second trimester (around 340 extra calories per day, per ACOG). First trimester nutrition is about quality, not quantity.

Can I take folic acid and a prenatal vitamin at the same time?

For most women, a prenatal vitamin with 400 to 800 mcg of folic acid is sufficient. Some women with specific risk factors (previous pregnancy with neural tube defects, certain medications, or MTHFR gene mutation) may be advised to take additional folic acid. Discuss with your provider what's right for your situation.

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